fix[react-devtools-fusebox]: add extension globals to build (facebook#32297)

We started using these globals in `react-devtools-shared/src/frontend`
code, forward-fixing facebook#32262.

Author: hoxyq

packages/react-devtools-fusebox/webpack.config.frontend.js

@@ -83,6 +83,9 @@ module.exports = {
       __PROFILE__: false,
       __TEST__: NODE_ENV === 'test',
       __IS_NATIVE__: true,
+      __IS_CHROME__: false,
+      __IS_FIREFOX__: false,
+      __IS_EDGE__: false,
       'process.env.DEVTOOLS_PACKAGE': `"react-devtools-fusebox"`,
       'process.env.DEVTOOLS_VERSION': `"${DEVTOOLS_VERSION}"`,
       'process.env.EDITOR_URL': EDITOR_URL != null ? `"${EDITOR_URL}"` : null,