Add communication channel to Module.webr object

Allows access to the communication channel from the worker thread even
once the worker script has been minified.

packages/webr/src/canvas.c

@@ -296,7 +296,7 @@ void canvasMode(int mode, pDevDesc RGD) {
             const canvas = Module.webr.canvas[$0];
             if (!canvas.capture) {
                 const image = canvas.offscreen.transferToImageBitmap();
-                chan.write({ type: 'canvas', data: {
+                Module.webr.channel.write({ type: 'canvas', data: {
                     event: 'canvasImage',
                     image,
                     id: $0,
@@ -347,7 +347,7 @@ void canvasNewPage(const pGEcontext gc, pDevDesc RGD)
 
     EM_ASM({
         if (!Module.webr.canvas[$0].capture) {
-            chan.write({ type: 'canvas', data: {
+            Module.webr.channel.write({ type: 'canvas', data: {
                 event: 'canvasNewPage',
                 id: $0,
             } });

src/webR/emscripten.ts

@@ -2,6 +2,7 @@ import type { RPtr, RTypeNumber } from './robj';
 import type { RObject, RList } from './robj-worker';
 import type { EvalROptions } from './webr-chan';
 import type { UnwindProtectException } from './utils-r';
+import type { ChannelWorker } from './chan/channel';
 
 export interface Module extends EmscriptenModule {
   /* Add mkdirTree to FS namespace, missing from @types/emscripten at the
@@ -127,6 +128,7 @@ export interface Module extends EmscriptenModule {
   // TODO: Namespace all webR properties
   webr: {
     UnwindProtectException: typeof UnwindProtectException;
+    chan: ChannelWorker | undefined,
     canvas: {
       [key: number]: {
         ctx: OffscreenCanvasRenderingContext2D;

src/webR/webr-worker.ts

@@ -866,6 +866,7 @@ function init(config: Required<WebROptions>) {
     UnwindProtectException: UnwindProtectException,
     evalR: evalR,
     captureR: captureR,
+    channel: chan,
     canvas: {},
 
     resolveInit: () => {