Add more options for DiscordRPC

[Noro95]

added more custom options & settings to the discordrpc
user can now customize

• app name (Playing xxx), by providing a custom discord app id instead of HGL's, falls back to HGL's if none provided
• activity title and state, now removable (empty string) and if undefined falls back to old ones
  and added title & state variables, {game} for game name & {platform} for platform/os name

hope i didn't miss/error in something, and always up for suggestions.

p.s. didn't do anything for images as they're already customizable enough :D
altho i do recommend making the small icon an image link instead of relying on discord's app assets, that is in case you think HGL would need more visibility with custom apps

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Use the following Checklist if you have changed something on the Backend or Frontend:

• Tested the feature and it's working on a current and clean install.
• Tested the main App features and they are still working on a current and clean install. (Login, Install, Play, Uninstall, Move games, etc.)
• Created / Updated Tests (If necessary)
• Created / Updated documentation (If necessary)

[flavioislima]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[Noro95]

I have read the CLA Document and I hereby sign the CLA

[Noro95]

also a heads up, CLA link in CONTRIBUTING.md is invalid

[flavioislima]

also a heads up, CLA link in CONTRIBUTING.md is invalid

ok, will check it out