Add setInterruptBuffer to public API, update changelog and docs

docs/project/changelog.md

@@ -42,6 +42,7 @@
   of Pyodide REPL in webpages (used in console.html) [#1125](https://github.com/iodide-project/pyodide/pull/1125) and [#1155](https://github.com/iodide-project/pyodide/pull/1155)
 - Flexible jsimports: it now possible to add custom Python "packages" backed by Javascript code, like the js package.
   The js package is now implemented using this system. [#1146](https://github.com/iodide-project/pyodide/pull/1146)
+- Added the `pyodide.setInterruptBuffer` API. This can be used to set a `SharedArrayBuffer` to be the keyboard interupt buffer. If Pyodide is running on a webworker, the main thread can signal to the webworker that it should raise a `KeyboardInterrupt` by writing to the interrupt buffer.
 
 ### Fixed
 - getattr and dir on JsProxy now report consistent results and include all names defined on the Python dictionary backing JsProxy. [#1017](https://github.com/iodide-project/pyodide/pull/1017)

docs/usage/api-reference.md

@@ -41,6 +41,7 @@ Backward compatibility of the API is not guaranteed at this point.
 | **{ref}`js_api_pyodide_runPython`**      | Runs Python code from Javascript.                              |
 | **{ref}`pyodide.runPythonAsync(code, ...) <js_api_pyodide_runPythonAsync>`** | Runs Python code with automatic preloading of imports.         |
 | **{ref}`js_api_pyodide_version`**        | The pyodide version string.                                    |
+| **{ref}`pyodide.setInterruptBuffer(interruptBuffer) <js_api_pyodide_setInterruptBuffer>`** | Set the keyboard interrupt buffer                |
 
 
 ```{eval-rst}

docs/usage/js-api/pyodide.setInterruptBuffer.md

@@ -0,0 +1,12 @@
+(js_api_pyodide_setInterruptBuffer)=
+# pyodide.setInterruptBuffer(interruptBuffer)
+This is a low level API for handling keyboard interrupts.
+Sets the pyodide interrupt buffer to be `interruptBuffer`. If thereafter one sets `interruptBuffer[0] = 2;` (2 stands for SIGINT) this will cause Pyodide to raise a `KeyboardInterupt`. The value of `interruptBuffer[0]` will regularly be set back to zero.
+This is intended for use when Pyodide is running on a webworker. In this case, one should make `interruptBuffer` a `SharedArrayBuffer` shared with the main thread. If the user requests a keyboard interrupt from the main thread, then the main thread can set `interruptBuffer[0] = 2;` and this will signal the webworker to raise a KeyboardInterupt exception.
+
+
+**Parameters**
+
+| name               | type       | description                                          |
+|--------------------|------------|------------------------------------------------------|
+| *interruptBuffer*  | TypedArray | The SharedArrayBuffer to use as the interrupt buffer |

src/pyodide.js

@@ -315,6 +315,7 @@ globalThis.languagePluginLoader = new Promise((resolve, reject) => {
     'version',
     'registerJsModule',
     'unregisterJsModule',
+    'setInterruptBuffer',
   ];
 
   function makePublicAPI(module, public_api) {