Feature searchbar

[thibmeu]

Search bar in Navigation bar.

What has been done:

• Design search component cards
• Better filtering of category
• No distinction between pages and categories. Categories have a main page.
• Dedicated search page
• Accessible through the whole website in the navigation bar and takes full width

To be done:

• search tags have to be better place. Maybe nearby difficulty dropdown. This should be done in another issue

Closes #37

[severus-sn4pe]

When entering more than one search term, combine category filters with is displayed in a hugh font size. This also overlaps the difficulty filter.