Update to Bootstrap 5.3 (Chameleon 5.x)

[malberts]

Chameleon is currently using Bootstrap 4.6 via Extension:Bootstrap.

The latest Bootstrap 4.6.2 is considered end of life as of January 1, 2023.

Before any meaningful work can start on this we need to get Extension:Bootstrap updated to Bootstrap 5.3: ProfessionalWiki/Bootstrap#67.

Part of the updates to the Chameleon dependencies (SCSS + Extension:Bootstrap) is to raise all minimum versions to:

• PHP 8.0
• MediaWiki 1.39

This will apply to Chameleon 5.x as well, since MW 1.35 will be end of life in September 2023 and it will be nice to get rid of a bunch of compatibility code.

This task is basically to get the current state of Chameleon working with Bootstrap 5.3. At a minimum this should just be styles, JavaScript and HTML. Bootstrap 5.3 introduces new features (e.g. color modes) which I do not think should be catered for explicitly in this initial update of Chameleon