Release redesign

[kantord]

Remaining tasks (for @kantord):

• [ ] ChallengeScreen.svelte / NavBarChallenge.svelte: Move progress bar from ChallengeScreen to NavBarChallenge
• [ ] NavBarChallenge.svelte: Link "xmark" icon to course (replaces "Cancel" button)
• [ ] SkillCard/ContentLeft.svelte / ImageSet.svelte: Remove ImageSet
• [ ] SkillCard/index.svelte: Add has-image class to skill-cards__skill-card if an image exists for the skill
• [ ] routes/index.svelte: Add text highlight to index.subtitle translation to match: A community-driven <b class="text-highlight">language-learning platform</b>
• [ ] VirtualKeyboard.svelte / HorizontalScroller.svelte: HorizontalScroller isn't working as expected (classes were renamed, styles were moved), hiding VirtualKeyboard
• [ ] 'Phrase.svelte`: Find a solution for and implement tooltips
• [ ] Move CSS into components
• [ ] Re-implement SASS variables as a theme (if needed)
• [ ] Revisit unused components: Title, ImageSet
• [ ] Update existing translations
• [ ] Update tests
• [x] Merge main branch

Other tasks if there's time (for @sandraor):

• [ ] Highlight correct and incorrect solutions to challenges
• [ ] Design for language learning selector
• [ ] Design for app language selector

[kantord]

@allcontributors please add @sandraor for design and code

[allcontributors[bot]]

@kantord

I've put up a pull request to add @sandraor! :tada: