Add support for web midi

[robertmuth]

the subject line says it all.

[srujzs]

Duplicate of #209

These were removed in 3f1285e#diff-7ce7b697c81d09379180b213c810f433c5f668e21c180651aa7876f48340669b when we planned on only supporting APIs that are supported by Chrome, Safari, and Firefox. #209 should add them back as these APIs are on the standards track and not experimental.

[srujzs]

Should be in the next major release now that #209 is closed.