refactor(better-moodle): complete rewrite with advanced tools

[jxn-30]

This closes #168. This closes #75.

Changes

More info & description coming here soon

TODO

• Find a system/class to create features & feature groups
  • How are uni-specific partial features implemented / configured?
• Find a system to create settings for features
  • How can settings be migrated (e.g. new setting key)?
• migrate all features/settings
  • updateNotification, update button & version spans
  • language
  • highlightNewSettings & highlightNewSettings.navbar
  • fullwidth
  • externalLinks
  • truncatedTexts
  • bookmarkManager
  • noDownload
  • eventAdvertisements
  • christmasCountdown
  • speiseplan
  • googlyEyes
  • semesterzeiten
  • prideLogo
  • quickRoleChange
  • darkmode
  • dashboard courseListFilter
  • dashboard courseListFavouritesAtTop
  • myCourses boxesPerRow
  • myCourses navbarDropdown & navbarDropdownFilter
  • myCourses navbarDropdownFavouritesAtTop
  • courses grades & gradesNewTab
  • courses collapseAll
  • courses imgMaxWidth
  • courses imageZoom
  • courses hideSelfEnrolHint
  • clock
  • weather
  • messages sendHotkey
  • messages markdown
  • nina
• migrate the NEW!-Badges of settings
• improve loading performance of V2 / append settings icon earlier
• create / update CI scripts for building and releasing
  • use commit statuses
  • require status checks before merging
  • do not abort all builds when one build fails (except on releasing)
• check that all aliases for settings are set correctly
• update CONTRIBUTING.md
• update README.md
• run ESLint and prettier on built userscript
• Transpile code for more browser compatibility and/or include polyfills for CSS and JS
• List of supported browsers
  • Note in readme
  • Add list to Release?
  • Show warning in Better-Moodle if browser version not supported

Things we MUST NOT forget to test (incomplete list)

• complete fresh instalation
• migrating an installation from v1

Notable Changes

We need this section as a small reminder on what to put into the changelog

Features

• linkIcons
• most settings don't require a reload anymore (Seiten-Reload nach Ändern von Einstellungen nur, wenn nötig vornehmen #75)
• when marking new settings as seen, only visible settings are marked as seen
• implemented a search function in Better-Moodle settings

Bugfixes

• marquee will not cause random flickers anymore

Refactoring

• complete rewrite for better maintainability, easier contribution and easier customization to other unis ([Refactor]: use a class based system for features #168 )
• make more use of moodle native functions
• ease the way for more integrating Better-Moodle into a customizable dashboard (Layout des Dashboards anpassen #16)
• increased generall accessibility of Better-Moodle (Accessibility erhöhen #76)
• cleaned up userscript storage