Breakout top navigation bar

[simondereuver]

Breakout the top navigation bar to its own html file, later used for each file with JS script to display the navigation bar on each page.

• [x] Create .html and .css files for topnavbar
• [x] Implement code

[simondereuver]

Created the files and implemented the code for the topnavbar, can now be dynamically used and fetched by all pages.