[Arduino IDE] Document how to build using Custom.h in Arduino IDE

See: [forum](https://www.letscontrolit.com/forum/viewtopic.php?f=4&t=7980)

docs/source/Participate/ArduinoIDE.rst

@@ -0,0 +1,87 @@
+Arduino IDE
+***********
+
+The preferred way to build ESPEasy is using PlatformIO.
+However, there are still lots of people happily using Arduino IDE.
+Therefore we try to keep the project source compatible with Arduino IDE.
+
+Since development is not done in Arduino IDE, it may happen that some commit breaks Arduino IDE compatibility.
+Usually it is something as simple as an include not being relative compared to the file which is being compiled.
+This is a bug, which PlatformIO does not complain about and thus can be missed easily during development.
+
+If something like this happens, please open an issue (or pull request) for it on GitHub.
+Also, if someone knows a build flag for PlatformIO to signal those errors, please let us know.
+
+
+Prepare Arduino IDE
+===================
+
+When installing Arduino IDE, its default installation folder structure is to share libraries and sketches among all installations of Arduino IDE.
+If you only build one project, this is just fine. 
+However, if you try to build several projects or versions of projects, then you will run into library dependency issues.
+
+See: `how to create portable version of Arduino IDE <https://www.arduino.cc/en/Guide/PortableIDE>`_
+
+For building ESPEasy it is adviced to use a "portable installation" of Arduino IDE.
+
+
+Arduino IDE Prerequisites
+=========================
+
+For building ESPEasy in Arduino IDE, you need to install the board manager and ESP8266/ESP32 library.
+
+See these excellent tutorials:
+
+* `How to install ESP8266 board for Arduino IDE <https://randomnerdtutorials.com/how-to-install-esp8266-board-arduino-ide/>`_
+* `How to install ESP32 board for Arduino IDE <https://randomnerdtutorials.com/installing-the-esp32-board-in-arduino-ide-windows-instructions/>`_
+
+
+Download ESPEasy Sources
+========================
+
+The sources can be downloaded from `GitHub <https://github.com/letscontrolit/ESPEasy>`_ as ZIP file.
+
+In this document, the given file system paths refer to a portable installation of Arduino IDE in ``D:\temp\Arduino-EspEasy\``
+
+The structure in the ZIP file are made for use in PlatformIO.
+To use the source in Arduino IDE, you have to split the sources into 2 parts:
+
+* The used libraries: ``D:\temp\Arduino-EspEasy\portable\sketchbook\libraries``
+* The source code: ``D:\temp\Arduino-EspEasy\portable\sketchbook\ESPEasy``
+
+Some used libraries differ from the original ones to make them work with ESPEasy.
+So make sure to use the ones supplied in the ZIP file in the ``lib`` folder.
+If some libraries are missing from the ``lib`` folder, you can install them via the Arduino IDE library manager.
+
+The source code files to be placed in the ``ESPEasy`` directory must be taken from the (first) ``src`` directory in the ZIP file.
+Meaning the file ``ESPEasy.ino`` must be in the ``ESPEasy`` folder. (including all files in sub folders)
+
+
+Building using Custom.h
+=======================
+
+There is a ``Custom-sample.h`` file supplied, which has lots of defines that can be set or uncommented to make a specific build 
+including just the plugins and controllers needed and maybe even some proper default settings.
+
+To use this file, it must be renamed to ``Custom.h``.
+PlatformIO does recognize the presence of this file when building a ``Custom`` build environment.
+But for Arduino IDE, a single line must be uncommented in ``ESPEasy_common.h``
+
+Make sure to uncomment this line at the start of ``ESPEasy_common.h``: ``//#define USE_CUSTOM_H``
+This define makes sure the ``Custom.h`` file is actually included during build.
+
+
+Board definitions
+=================
+
+In Arduino IDE you must prepare the environment variables yourself.
+
+.. image:: ArduinoIDEBoardConfig.png
+
+* Board: "Generic ESP8266 Module"
+* Flash Size: Pick the one reflecting your board (4M flash 1M FS is the most used)
+* Flash Mode: "DOUT"
+
+The other settings are likely to be correct when using the defaults.
+See the screenshot to be sure.
+

docs/source/index.rst

@@ -30,6 +30,7 @@ Welcome to ESP Easy's documentation!
    :caption: Appendix
 
    Participate/PlatformIO.rst
+   Participate/ArduinoIDE.rst
    Participate/Documentation.rst
    Participate/ProjectStructure.rst
    Reference/Safety.rst

src/ESPEasy.ino

@@ -7,6 +7,11 @@
 #pragma GCC diagnostic warning "-Wall"
 #endif
 
+// Include this as first, to make sure all defines are active during the entire compile.
+// See: https://www.letscontrolit.com/forum/viewtopic.php?f=4&t=7980
+// If Custom.h build from Arduino IDE is needed, uncomment #define USE_CUSTOM_H in ESPEasy_common.h
+#include "ESPEasy_common.h"
+
 // Needed due to preprocessor issues.
 #ifdef PLUGIN_SET_GENERIC_ESP32
   #ifndef ESP32

src/ESPEasy_common.h

@@ -1,6 +1,14 @@
 #ifndef ESPEASY_COMMON_H
 #define ESPEASY_COMMON_H
 
+// *****************************************************************************************
+// For Arduino IDE users:
+// When building using Custom.h, uncomment the next line:
+//#define USE_CUSTOM_H
+// *****************************************************************************************
+
+
+
 #include <stddef.h>
 namespace std
 {
@@ -12,14 +20,13 @@ namespace std
 #include <Arduino.h>
 #include <string.h>
 
-#include "src/Globals/RamTracker.h"
-
 // User configuration
 // Include Custom.h before ESPEasyDefaults.h. 
 #ifdef USE_CUSTOM_H
 #include "Custom.h"
 #endif
 
+#include "src/Globals/RamTracker.h"
 #include "src/DataStructs/ESPEasyDefaults.h"
 
 #ifdef USE_LITTLEFS