pass along additional props supplied to the Markdown component

[quantizor]

closes #171

[codecov]

Codecov Report

Merging #174 into master will increase coverage by 0.11%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #174      +/-   ##
==========================================
+ Coverage   99.71%   99.82%   +0.11%     
==========================================
  Files           1        1              
  Lines         345      569     +224     
  Branches       51       96      +45     
==========================================
+ Hits          344      568     +224     
  Misses          1        1

Impacted Files	Coverage Δ
index.js	99.82% <100%> (+0.11%)	⬆️

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