Rework web assembly inclusion

This moves the .wasm file out of the static/js/ folder and into the
source tree. This way we can import it and webpack will pick it up
and version the file with a hash.

This fixes possibly running with an out of date file from the browser
cache and also fixes running offline.

The file extension had to be changed because there is a default rule in
webpack that matches the .wasm extension and causes the following error:

    Failed to compile.

    ./src/sagas/mpy-cross.wasm
    Module parse failed: magic header not detected
    File was processed with these loaders:
    * ./node_modules/file-loader/dist/cjs.js
    You may need an additional loader to handle the result of these loaders.
    Error: magic header not detected

The webpack configuration cannot be modified without ejecting
create-react-app or using something like react-app-rewired, which we
would like to avoid.

Also using ncp to copy file now which fixes building on Windows.

src/react-app-env.d.ts

@@ -5,6 +5,11 @@ declare module '*.json' {
     export default src;
 }
 
+declare module '*.emcwasm' {
+    const src: string;
+    export default src;
+}
+
 declare module '*.zip' {
     const src: string;
     export default src;

src/sagas/.gitignore

@@ -0,0 +1 @@
+*.emcwasm

src/sagas/mpy.ts

@@ -9,6 +9,7 @@ import {
     didCompile,
     didFailToCompile,
 } from '../actions/mpy';
+import wasm from './mpy-cross.emcwasm';
 
 /**
  * Compiles a script to .mpy and dispatches either didCompile on success or
@@ -17,7 +18,13 @@ import {
  */
 function* compile(action: MpyCompileAction): Generator {
     const result = (yield call(() =>
-        mpyCrossCompile('main.py', action.script, action.options),
+        mpyCrossCompile(
+            'main.py',
+            action.script,
+            action.options,
+            // HACK: testing user agent for jsdom is needed only for getting unit tests to work
+            navigator.userAgent.includes('jsdom') ? undefined : wasm,
+        ),
     )) as CompileResult;
     if (result.status === 0 && result.mpy) {
         yield put(didCompile(result.mpy));