Build system fixes & Discord RPC update

[ThePotato97]

Cleaned up the build process so it actually works without manual trial and error. Also updated Discord RPC fields.

Build stuff:

• Added vcpkg.json so dependencies install themselves.
• Forced CMake to pre-download NASM from a mirror because the official site keeps timing out.
• Made CMake auto-extract the mpv dll and auto-apply the discord-rpc patch.
• Defaulted build folder to out/.

Discord RPC:

• Flattened the buttons (no more arrays/nested structs).
• Added new activity fields (name, statusDisplayType, etc).
• Added status display type constants.
• Updated SetDiscordVideoPresence, SetDiscordDiscoverPresence, and SetDiscordMetaDetailPresence to actually use the new display types.

CI & Other stuff:

• Added a proper .gitignore so the repo stays clean.

just run cmake -S . -B out and it should build fine.

[Zaarrg]

thanks for the amazing pr, will review and merge when i have time