GameScope: Add Mouse Sensitivity

[sonic2kk]

GameScope has recently added support for configuring mouse sensitivity with ValveSoftware/gamescope@8783464. This is a decimal value that the base mouse sensitivity is multiplied by. This PR exposes it on our GameScope GUI.

This option didn't seem to do anything in my tests, both from the SteamTinkerLaunch GUI and manually with games from the commandline. I am using the right version as the option shows up in --help.

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TODO:

• Further testing
• Update langfiles
• Update wiki screenshot

[sonic2kk]

It will go in a seperate PR, but I am going to refactor how we index the arrays. It's getting way too annoying to change each index when we bump an option.

[sonic2kk]

Something strange is going on. When --adaptive-sync is enabled, GSMOUSESENSITIVITY is set to --. Otherwise, it works fine.

Something weird is going on, potentially related to #1024.

[sonic2kk]

Weirdness should be fixed with #1027.

In that PR I used the example of -r and --rt, but here the issue is likely related to the -s in --adaptive-sync (-sync -> -s).

[sonic2kk]

Rebased on master after #1027, fixed an issue where we were trying to compare decimals, and the weirdness is gone.

Game launch works OK in my tests too with this option, and when the option is 1, we correctly ignore it and don't append it to the GameScope arguments. It also seems to have an effect with Steam games, unlike my earlier tests.

I will update the langfiles and bump the version and then merge.

[sonic2kk]

Langfiles updated, version bumped, shellcheck is green, we are ready to merge!