Finish preparing Pegasus container

[redbeardymcgee]

Currently the Pegasus container works great, but it is not complete. Documentation was added for the ROMs dir, but BIOS files have not been documented yet. Before simply adding documentation, I want to make sure we know how we intend to handle these files. Should this be lifted to the environment, such as WOLF_EMU_BIOS_DIR? Should it just be documented as a member of the mounts list in wolf's config.toml?

Additionally, Pegasus requires the user to prepare metadata files on their own. It is not packaged with any fetchers. I think we may use this one but should we add this to the container or document how to use it with wolf?

Hotkey configuration is also an important feature. Some way to at least exit the current emulator and return to the frontend is mandatory. This requires pre-configuration for each individual emulator, and 1 for retroarch as a whole.

Not all emulators require BIOSes, but some require different files that need to be installed or configured.

The launchers for the emulators themselves in Pegasus are important for getting to the emulator directly when needed. They should have some images associated and maybe other potential metadata if supported, to make them fit in with a launcher frontend.