Rewrite it

[GarboMuffin]

The changes:

• Sensitive pages no longer use file:// (we will need one file:// for migration unfortunately)
• Most pages use separate protocols entirely so eg. packager and editor won't misbehave with eachother
• IPC, permissions, and preload are now per-window
• Renderer processes no longer receive full paths (just names and numbers)
• Clamped down preload scripts to only expose what's actually needed, not the entire IPC surface area
• L10N strings now use structured JSON so we can add context

What's missing:

• custom confirm() alert() because Electron vanilla are still broken
• offline library files
• offline extensions
• window background colors
• escape to close subwindows, also make sure it doesnt interfere with fullscreen escape
• addon splash dark mode
• update download dialogs
• new update checker
• selected microphone
• selected camera
• hardware acceleration toggle
• sleep hidden windows toggle
• bypass CORS toggle
• open user data button
• content security policies
• userscript & userstyle
• update privacy policy
• desktop settings warnings
• remember last accessed directory and migrate old
• listen for locale changes in renderer, forward to main, persist, migrate old
• handle what happens when the migrate window is closed
• packager preview
• load project by URL
• test mailto:
• username
• scratch link DNS?
• mac test 1: selected microphone was blank, disabled update checker did not migrate
• prompt()
• detect ARM translation
• handle create data: window?
• test represented file & changed on macOS
• Update CI
• make sure that windows really really do not navigate
• test file opening on macOS
• selected microphone and camera actually wont work right now, ids differ between origins
• l10n in renderers
• normalize.css
• remove debug logging
• Put the entire extension gallery into the library scratch-gui#804
• migrating old settings and such (very scary)
• a whole bunch of testing