Search polish

[colszowka]

Followup to #84 to do some non-MVP-but-still-nice-to-have additions for the search:

• More expansive tests - Via Announcement post for project sorting #372 and Search results pagination #375
• Result Pagination - Via Search results pagination #375
• When submitting an empty form on desktop, the page is very bleak. It should show at least some "please add a query message or so". On mobile this problem is not that prominent since the search input form is full-width and large there. - Via Search UI tweaks #376
• Similar issue when submitting a query with 0 results - Via Search UI tweaks #376
• Focus the form input on initial access (or empty query) on mobile - Via Search UI tweaks #376
• Put the button into bulma's loading state after submit - Via Search UI tweaks #376

[colszowka]

Adressed via #372, #375 and #376, closing. Further improvements to search, i.e. relating to result relevance, will take place in separate, future PRs.