Ability to reset individual `@storybook/addon-controls` controls

[emattias]

Right now you can reset all controls by pressing this button:

Sometimes I want to reset only one field. Please add that ability

[seanmaisch]

Agreed, I would like this as well please, especially when dealing with stories with lots of controls configured and you only want one reset (like a color).

[lucapollani]

Agree on this, dealing with this kind of controls like "text" when there's not a default value, there's not actually the possibility to reset them to "undefined", the will always pass empty string at least.

Here I cannot get back to previous state:

PS. Probably need to add the label "addon: controls" to the issue in order to track it better.