Please re-enable the built-in "Rust" package when the package is getting uninstalled

[FichteFoll]

Rust Enhanced auto-ignores the Rust package on installation.

rust-enhanced/cargo_build.py

Lines 636 to 639 in dec2e11

	if 'Rust' not in ignored:
	ignored.append('Rust')
	settings.set('ignored_packages', ignored)
	sublime.save_settings('Preferences.sublime-settings')

While I don't know if there is any reason for it to still do that after the built-in Rust package has received a lot of updates over the past years, including merging in many changes from here, please add some code that un-ignores the package again when the package is uninstalled again.

See https://packagecontrol.io/docs/events for docs.

This obviously has limitations and will only be run when the package is enabled and is uninstalled via Package Control's command, but it should still help prevent people running into situations where they don't have any Rust highlighting at all.