Support to change primary color in ThemeModifier

[zilliuscon]

Pre-Request Checklist

• I have checked Playnite's settings (e.g., in Settings -> Appearance) and confirmed that this change cannot be made there.
• I have checked that this feature is not already available using the ThemeModifier plugin.

Feature Description

the color of the highlighted game part that's purple would be really neat if you could change it thememodifier,

Screenshots or Mockups

No response