Various fixes for upstream

[claravanstaden]

• Adds markdown linter to match polkadot-sdk, fixes markdown files
• Standarize rustfmt config to match polkadot-sdk
• Fix bug in subtree script
• Add licenses
• Fix rust fmt

polkadot-sdk companion: Snowfork/polkadot-sdk#67

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (63906dd) 81.29% compared to head (d73f3ac) 81.29%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1057   +/-   ##
=======================================
  Coverage   81.29%   81.29%           
=======================================
  Files          54       54           
  Lines        2240     2240           
  Branches       71       71           
=======================================
  Hits         1821     1821           
  Misses        402      402           
  Partials       17       17           

Flag	Coverage Δ
rust	81.45% <ø> (ø)

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[vgeddes]

+1