💄 [#1467] Fix logo stretching in Safari and position of Search

[jiromaykin]

Note: the logo stretching problem can only be reviewed in Safari (Browserstack).
PNG and other images stretch on both desktop and mobile (SVG's remain the same)-> this PR should solve that problem.
everything else can be reviewed in all browsers.

• set logo to static height for mobile and desktop
• decrease header margin bottom, make logo smaller in header
• improve search bar margins for mobile in all browsers
• increase space in mobile menu between icons and page-titles

(NB: on very tiny screens the logo will become smaller when the mobile menu is opened because the scrollbar appears, taking up horizontal space).

[codecov-commenter]

Codecov Report

Merging #628 (a2ec139) into develop (d1e4c71) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop     #628   +/-   ##
========================================
  Coverage    96.51%   96.51%           
========================================
  Files          600      600           
  Lines        20684    20684           
========================================
  Hits         19964    19964           
  Misses         720      720           

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