Encourage contribution from community through the package itself

[moodymudskipper]

Editing a csv on github is not something many will take the trouble to do, but we could :

• have a function to upload our input on a given error/warning if argh doesn't have any yet, or if we think it's incomplete or that we can do better.
• be able to call this function / a variant of it conveniently just after the error : report_on_last_error("You might have attached package plyr after dplyr and called plyr::summarize instead of dplyr::summarize")
• have the possibility to opt in to have a message proposing us to upload one, each time we get an error, so we don't procrastinate and think "I should document this error later", then never do it.

These entries would then be reviewed manually as they are now, and incorporated in the package as it goes.