[FEAT] Hide When Not Focused

[leviFrosty]

Hey! Thanks for creating this plugin, it's well-documented and easy to use.

Feature request: I find it not intuitive when using the delay option that the previous blame sticks to the previously focused line.

Solution: Add config option to hide on blur (after losing focus of current line). This feature would make the previously shown blame instantly hide after moving from that line.

If you don't have much time to implement this, perhaps I could take a crack at it. I don't know much about Lua, so I don't feel comfortable making a PR.

Best, Levi