Update doc for `mason register`

[mattrabe]

The online docs list the registration commands for bootanimation and splash like so:

mason register media bootanimation [NAME] [VERSION]

But according to the cli (mason register media bootanimation -h) the correct commands are like this:

mason register media bootanimation [OPTIONS] NAME VERSION MEDIA

Similarly, apk is listed in the online docs as:

mason register apk [NAME] [VERSION]

But according to the cli it should be:

mason register apk [OPTIONS] APKS...

Similarly, config is listed in the online docs as:

mason register config [NAME] [VERSION]

But according to the cli it should be:

mason register config [OPTIONS] CONFIGS...