feat: add preliminary main sidebar
- Add new tree-based main sidebar which serves as global navigation for the site
- Add buttons to trigger the sidebar appearing on mobile
- Update styles for ex. Main sidebar,
ProjectCard.tsx
,Tag.tsx
etc. - Move
ThemeMenu.tsx
to the<Footer>
- Add new icons
- Enforce Astro validation for
image_alt
in the Project collection to not contain the words 'image', 'picture', or 'photo' - Other misc changes