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).
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