A few additional theme elements

Thank you for your work! I haven't tried alternatives yet, but your client is definitely good.

There are a few suggestions about the elements of the theme.

The `disabled_fg` affects both unselected tabs and disabled commands in the bar, which in the absence of elements fg and bg for unselected tabs and bg element for disabled commands in the bar limits the customization options.

The `tag_fg` and `branch_fg` elements ignore `selection_fg` while the `commit_hash`, `commit_time` and `commit_author` do not, which definitely gives a better result.