feat: Add subpath export for initializeInpageProvider.cjs

Add a subpath export for the `initializeInpageProvider.cjs` file. This
allows projects with legacy build systems to import this file directly,
which can be useful for reducing bundle size (especially for build
systems without tree shaking).

The `metamask-extension` project uses two build systems: one which
obeys export maps, one which ignores them (Webpack and browserify
respectively). The existing `initializeInpageProvider` export map entry
doesn't work for browserify because it's looking for
`initializeInpageProvider.js`. The file extension is wrong.

package.json

@@ -49,6 +49,10 @@
         "default": "./dist/initializeInpageProvider.cjs"
       }
     },
+    "./dist/initializeInpageProvider.cjs": {
+      "types": "./dist/initializeInpageProvider.d.cts",
+      "default": "./dist/initializeInpageProvider.cjs"
+    },
     "./stream-provider": {
       "import": {
         "types": "./dist/StreamProvider.d.mts",