editor: add basic intellisense

This adds basic intellisense for code completion and function signatures
using the Python `jedi` package running in a Pyodide environment.

src/pybricksMicropython/python-message.ts

@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2022 The Pybricks Authors
+
+import { createAction } from '../actions';
+
+// NB: although we are using the same action creator as we do for redux, these
+// actions are not used by redux but rather are to sent between workers.
+
+/**
+ * Message sent from main to work to request initialization of Pyodide.
+ */
+export const pythonMessageInit = createAction(() => ({
+    type: 'python.message.init',
+}));
+
+/**
+ * Message sent from worker to main that indicates {@link pythonMessageInit}
+ * succeeded.
+ */
+export const pythonMessageDidInit = createAction(() => ({
+    type: 'python.message.didInit',
+}));
+
+/**
+ * Message sent from worker to main that indicates {@link pythonMessageInit}
+ * failed.
+ */
+export const pythonMessageDidFailToInit = createAction((error: Error) => ({
+    type: 'python.message.didFailToInit',
+    error,
+}));
+
+/**
+ * Message sent from main to worker to set the shared interrupt buffer.
+ */
+export const pythonMessageSetInterruptBuffer = createAction((buffer: Uint8Array) => ({
+    type: 'python.message.setInterruptBuffer',
+    buffer,
+}));
+
+/**
+ * Message sent from main to worker to request code completion.
+ */
+export const pythonMessageComplete = createAction(
+    (code: string, lineNumber: number, column: number) => ({
+        type: 'python.message.complete',
+        code,
+        lineNumber,
+        column,
+    }),
+);
+
+/**
+ * Message sent from worker to main that indicates {@link pythonMessageComplete}
+ * succeeded.
+ */
+export const pythonMessageDidComplete = createAction((completionListJson: string) => ({
+    type: 'python.message.didComplete',
+    completionListJson,
+}));
+
+/**
+ * Message sent from worker to main that indicates {@link pythonMessageComplete}
+ * failed.
+ */
+export const pythonMessageDidFailToComplete = createAction((error: Error) => ({
+    type: 'python.message.didFailToComplete',
+    error,
+}));
+
+/**
+ * Message sent from main to worker to request function signature.
+ */
+export const pythonMessageGetSignature = createAction(
+    (code: string, lineNumber: number, column: number) => ({
+        type: 'python.message.getSignature',
+        code,
+        lineNumber,
+        column,
+    }),
+);
+
+/**
+ * Message sent from worker to main that indicates {@link pythonMessageGetSignature}
+ * succeeded.
+ */
+export const pythonMessageDidGetSignature = createAction(
+    (signatureHelpJson: string) => ({
+        type: 'python.message.didGetSignature',
+        signatureHelpJson,
+    }),
+);
+
+/**
+ * Message sent from worker to main that indicates {@link pythonMessageGetSignature}
+ * failed.
+ */
+export const pythonMessageDidFailToGetSignature = createAction((error: Error) => ({
+    type: 'python.message.didFailToGetSignature',
+    error,
+}));