Allow including SVG in MarkupContent

Created by: felixfbecker

This enables code insights with available graphs (e.g. CodeCov). Any <script>, onclick etc will still be sanitized, we are using a whitelist of elements. This may need to be expanded in the future.

This also:

• Makes our markdown follow how GitHub renders markdown files, not markdown comments with regard to line breaks
• Allows HTML titles (tooltips)

Created by: codecov[bot]

Codecov Report

Merging #10206 into master will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master   #10206   +/-   ##
=======================================
  Coverage   43.37%   43.37%           
=======================================
  Files        1386     1386           
  Lines       76150    76151    +1     
  Branches     6681     6682    +1     
=======================================
+ Hits        33030    33031    +1     
  Misses      40113    40113           
  Partials     3007     3007           

Flag	Coverage Δ
#unit	43.37% <100.00%> (+<0.01%)

Impacted Files	Coverage Δ
shared/src/util/markdown.ts	74.07% <100.00%> (+0.99%)