Support more media keys

[akhilman]

These are keys I care about:

• KEY_MEDIA
• KEY_PLAYER
• KEY_EMAIL
• KEY_HOMEPAGE
• KEY_POWER
• KEY_SLEEP

But perhaps it will be more useful to add a way to enter the raw keycodes, like #116 or $116.

[jtroo]

Being able to enter raw numbers seems like it could be useful. You may have looked at the code a bit and guessed this already, but some reasons for why this hasn't been done yet:

• all keys have two types: an "operating system" type and a "keyberon" type
  • the mapping between the two key types is currently static, e.g. in impl From<KeyCode> for OsCode
• using raw keycode numbers is not cross-platform since different OSs use different numbers for the keys

In any case, a PR is now open for these keys. I haven't tested the code at all though.

[jtroo]

Closing for lack of activity, with the code changes being merged.