Tag alias: unbuttoning -> partially_unbuttoned_

create alias unbuttoning -> partially_unbuttoned

Link to alias

Both tags are close enough & not very populated atm.

*edit* messed up the alias request with an errant underscore.

I think it's better to make
partially_unbuttoned -> unbuttoned
alias and leave unbuttoning separate.

This would be consistent with untied/untying and unzipped/unzipping tags.

Agreed with partially_unbuttoned -> unbuttoned , done.