Replaced all text in navbar by icons, moved TOC to the right of Home
button. TOC is now correctly displayed with small animation. Added black
theme to light and dark themes.
langue.phundrak.com now runs using the `webdev` tool from Dart.
Javascript code has been replaced with Dart code, and CSS code has
been replaced with SCSS code. To run the project, execute
`webdev serve` at the project’s root.