Steam on Windows: Add playback registry keys so .aarec files automatically playback with a doubleclick

Steam Docs for install scripts: https://partner.steamgames.com/doc/sdk/installscripts

Registry keys: https://gitlab.com/armagetronad/build_codeblocks/-/blob/legacy_0.2.8/armagetronad.nsi

  WriteRegStr HKCR ".aarec" "" "ArmagetronAd.Recording"
  WriteRegStr HKCR "ArmagetronAd.Recording" "" "Armagetron Advanced Debug Recording"
  WriteRegStr HKCR "ArmagetronAd.Recording\shell\DefaultIcon" "" "$INSTDIR\armagetronad.exe,1"
  WriteRegStr HKCR "ArmagetronAd.Recording\shell\open\command" "" '"$INSTDIR\armagetronad.exe" --playback "%1"'

Where HKCR really is just Computer\HKEY_CLASSES_ROOT, and "" stands for (the key?) (DEFAULT).