This is the library we created to embed ROM files on Game Jolt for homebrew support.
It's basically a thin wrapper around Emularity to make it extremely easy to embed and use. It also includes the JS drivers and config files required for MAME. The JS drivers are built using the Emscripten target. The config files are generated by loading the particular driver into MAME, setting the key mapping, and exporting into a .cfg file.
View the scripts folder to see how the builds are done of the various drivers.
Each system supported must contain a "test" folder with a working example. The ROMs included in the test folder must be free to distribute.