treat `!pronouns <own-nickname> she/her` as a synonym for `!config user pronouns she/her`

[jesopo]

I've come across a lot of users of bitbot that have expected this format - shouldn't hurt to implement it but it will want a refactor of setting-related commands (!weather, !time, !pronouns, etc) in to a standardised format

Maybe I should look in to how other bots do changing user settings and pick some that are widespread and nice