Vectorize PNG artwork

[localspook]

The logo in the README is pretty pixelated, so this PR vectorizes it (and the rest of the artwork). The files are Inkscape SVGs.

I renamed catch2-logo-small*.png to catch2-logo-full*.svg because vector images don't really have an inherent size.

[localspook]

CI failure seems unrelated...

CMake Error at C:/Program Files (x86)/CMake/share/cmake-3.16/Modules/FindPackageHandleStandardArgs.cmake:146 (message):
  Could NOT find PythonInterp: Found unsuitable version "2.7.17", but
  required is at least "3" (found C:/Python27/python.exe)

[ChrisThrasher]

Can I ask how you vectorized these files?

[localspook]

Inkscape’s Trace Bitmap tool to start, then manual fixups for parts the tool didn’t do a good job on.

[ChrisThrasher]

Please rebase on the devel branch. It should fix CI. I would do this myself but I'm not allowed to because you opened the PR from your fork's trunk branch.

[localspook]

Rebased. I didn't know opening from trunk had that kind of restriction, I'll be more careful to create new branches in the future.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.98%. Comparing base (416b075) to head (12b698b).
Report is 1 commits behind head on devel.

Additional details and impacted files

@@           Coverage Diff           @@
##            devel    #2990   +/-   ##
=======================================
  Coverage   90.98%   90.98%           
=======================================
  Files         198      198           
  Lines        8599     8599           
=======================================
  Hits         7823     7823           
  Misses        776      776           

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[ChrisThrasher]

Thanks!