[SysVar] Add %c_random%(L,H) system variable

As requested on the [forum](https://www.letscontrolit.com/forum/viewtopic.php?p=73835#p73835)

docs/source/Reference/SystemVariable.rst

@@ -362,6 +362,9 @@ The conversion always outputs a string, but not all of these can be converted ba
    * - Secs to dhms: ``%c_s2dhms%(100000)``
      - Secs to dhms: ``1d03:46:40``
      - Seconds to days/hours/minutes/seconds notation
+   * - Random(L,H): ``%c_random%(0, 1)``
+     - Random(L,H): ``0.123``
+     - Generate random number in the given range L ... H (Added: 2025/04/29)
    * - To HEX: ``%c_2hex%(100000)``
      - To HEX: ``186A0``
      - Convert integer value to HEX notation.  (Added: 2020/10/07)

src/src/Helpers/ESPEasy_math.cpp

@@ -339,6 +339,7 @@ ESPEASY_RULES_FLOAT_TYPE mapADCtoFloat(ESPEASY_RULES_FLOAT_TYPE float_value,
                                        ESPEASY_RULES_FLOAT_TYPE out1,
                                        ESPEASY_RULES_FLOAT_TYPE out2)
 {
+  // FIXME TD-er: When ADC1/2 are equal, shouldn't we just output either out1, out2 or some average of those?
   if (!approximatelyEqual(adc1, adc2))
   {
     const ESPEASY_RULES_FLOAT_TYPE normalized = (float_value - adc1) / (adc2 - adc1);

src/src/Helpers/Hardware.cpp

@@ -526,6 +526,20 @@ long HwRandom(long howsmall, long howbig) {
     return HwRandom(diff) + howsmall;
 }
 
+ESPEASY_RULES_FLOAT_TYPE HwRandom_f(
+  ESPEASY_RULES_FLOAT_TYPE howsmall,
+  ESPEASY_RULES_FLOAT_TYPE howbig)
+{
+  if (approximatelyEqual(howsmall, howbig)) {
+    return howsmall;
+  }
+  return mapADCtoFloat(
+    HwRandom(),
+    0, std::numeric_limits<uint32_t>::max(),
+    howsmall, howbig);
+}
+
+
 #ifdef ESP8266
 void readBootCause() {
   lastBootCause = BOOT_CAUSE_MANUAL_REBOOT;

src/src/Helpers/Hardware.h

@@ -93,6 +93,11 @@ long     HwRandom(long howsmall,
                   long howbig);
 
 
+ESPEASY_RULES_FLOAT_TYPE HwRandom_f(
+  ESPEASY_RULES_FLOAT_TYPE howsmall,
+  ESPEASY_RULES_FLOAT_TYPE howbig);
+  
+  
 /********************************************************************************************\
    Boot information
  \*********************************************************************************************/

src/src/Helpers/StringConverter.cpp

@@ -1507,6 +1507,12 @@ void parseStandardConversions(String& s, bool useURLencode) {
   #endif
   SMART_CONV(F("%c_alt_pres_sea%"), toString(altitudeFromPressure(data.arg1, data.arg2), 2))
   SMART_CONV(F("%c_sea_pres_alt%"), toString(pressureElevation(data.arg1, data.arg2), 2))
+
+  #if FEATURE_USE_DOUBLE_AS_ESPEASY_RULES_FLOAT_TYPE
+  SMART_CONV(F("%c_random%"), doubleToString(HwRandom_f(data.arg1, data.arg2), 3, true))
+  #else
+  SMART_CONV(F("%c_random%"), floatToString(HwRandom_f(data.arg1, data.arg2), 3, true))
+  #endif
   #undef SMART_CONV
 }
 

src/src/WebServer/SysVarPage.cpp

@@ -378,6 +378,8 @@ void handle_sysvars() {
       F("Mins to hcm:  %c_m2hcm%(482)"),
       F("Secs to dhms: %c_s2dhms%(100000)"),
 
+      F("Random: %c_random%(0, 100)"),
+
       // addFormSeparator(3,
       F("To HEX: %c_2hex%(100000)"),
 

static/espeasy.js

@@ -175,7 +175,7 @@ var AnythingElse = [
   "%ethwifimode%", "%ethconnected%", "%ethduplex%", "%ethspeed%", "%ethstate%", "%ethspeedstate%",
   //Standard Conversions
   "%c_w_dir%", "%c_c2f%", "%c_ms2Bft%", "%c_dew_th%", "%c_alt_pres_sea%", "%c_sea_pres_alt%", "%c_cm2imp%", "%c_mm2imp%",
-  "%c_m2day%", "%c_m2dh%", "%c_m2dhm%", "%c_s2dhms%", "%c_2hex%", "%c_u2ip%", "%c_uname%", "%c_uage%", "%c_ubuild%", "%c_ubuildstr%",
+  "%c_m2day%", "%c_m2dh%", "%c_m2dhm%", "%c_s2dhms%", "%c_random%", "%c_2hex%", "%c_u2ip%", "%c_uname%", "%c_uage%", "%c_ubuild%", "%c_ubuildstr%",
   "%c_uload%", "%c_utype%", "%c_utypestr%",
   //Variables
   "var", "int"