Provide ability to update snapshot

[kylemh]

Currently, if there's a desired size mis-match, I'm required to:

• delete the file
• delete { matchSnapshot: true } from plugin config
• create build (new snapshot defined)
• re-add { matchSnapshot: true } to plugin config

This feels like it can be improved.

[TrySound]

I usually set matchSnapshot to true only in ci

[kylemh]

Ah I see. That makes more sense. Perhaps some tiny documentation reflecting that then? The naming of the variable indicated to me that it should always be true.

[TrySound]

Do you want to send a PR with clarification?