webextension: add support for options_page key

[fregante]

🙋 feature request

Chrome supports two keys to specify the options page:

• options_ui
• options_page

MDN reports that options_page is deprecated and so does Parcel's schema:

parcel/packages/transformers/webextension/src/schema.js

Line 289 in 53633df

// options_page is deprecated

However that doesn't reflect reality, Chrome does not deem the key deprecated in their docs and even Firefox eventually added support for it: https://bugzilla.mozilla.org/show_bug.cgi?id=1816960

You can find further reasoning in the bugzilla.

🤔 Expected Behavior

options_page should be equivalent to options_ui.page

😯 Current Behavior

The key is ignored and the specified options.html is not processed.

💻 manifest.json demo

{
	"$schema": "https://json.schemastore.org/chrome-manifest",
	"name": "options_page minimal extension",
	"version": "0.0.0",
	"manifest_version": 3,
	"options_page": "options.html"
}