✨ More mobile friendly, fix wrong URL, Hamburger menu

- Hamburger menu on mobile
- title is moved into header on mobile
- Smaller titles on mobile
- Fix wrong import of env in config
- Cleaned up unused imports

TODO.md

@@ -3,13 +3,19 @@
 ## Code
 - [ ] Temporal API or day.js for dates
 
+## SSE
+- [x] Correct Sitemap.xml
+- [x] Correct robots.txt
+- [x] Correct security.txt
+
 ## Layout
-- [ ] Show current page in navbar
+- [x] Show current page
 - [x] Correct bg colour on entire page
+- [x] Hamburger menu on mobile
 
 ## Accessibility
 - [ ] Fix colours on buttons
-- [ ] Correct contrast
+- [x] Correct contrast
 - [ ] All interactable elements have labels
 - [ ] Colour links, also in MDX posts