fix: add electron as an external for webpack

[devm33]

This should fix the issue where require('electron') does not resolve on the bundled extension after #238149

Note, I don't see how to bundle the extension locally to confirm that this is working.

cc #207867

[TylerLeonhardt]

due to the nature of this change, we will hold off on it til Monday so we can let it bake in Insiders.

[TylerLeonhardt]

You can trigger a bundled build by running:

npm run gulp vscode-darwin-arm64

Which will build the macOS ARM build.

You can see all of our targets with:

npm run gulp -- --tasks

[TylerLeonhardt]

I verified that the bundled code for GitHub & Microsoft auth extensions now require "electron"

[devm33]

I verified that the bundled code for GitHub & Microsoft auth extensions now require "electron"

Thank you for verifying! 🎉