Add RFC: OBS UI Panel APIs

[mitchlloyd]

Description

Provide the JS Bindings API described in the obs-browser readme to browser-panels (docked UI panels).

Motivation and Context

Unifying the exposed JS APIs between obs-browser-source and browser-panel is the first step toward allowing third-party developers to control OBS with docked panel UI.

Link to RFC

[derrod]

Note the link in your PR no longer points to the correct commit, simply replace the commit hash with the branch in the URL like so: https://github.com/mitchlloyd/obs-rfcs/blob/browser-panel-js-apis/text/0000-browser-panel-js-apis.md