selected_tab in theme.ron might not do anything

[star-szr]

Describe the bug
The selected tab does not appear to be overrideable via the theme. (theme.ron has a selected_tab key)

To Reproduce
Steps to reproduce the behavior:

1. Edit theme.ron to change selected_tab to something wacky (I suggest Red or Magenta or Cyan)
2. Launch gitui
3. Open up various parts of the UI, and check for your color override (I couldn't find it anywhere)

Expected behavior
I would expect the selected tab (on launching gitui this should be "Status") to take the selected_tab value from the theme.ron config.

Screenshots

Screenshots from v0.2.6 (before initial color theme support was added)

Context (please complete the following information):

• OS/Distro + Version: Pop!_OS 20.10
• GitUI Version: v0.15.0
• Rust version: Not sure, but probably not relevant in this case. I installed gitui via nixpkgs but I can reproduce the behaviour by building gitui from source.

Additional context

Screenshots from v0.10.1 (after theme support was added, but before the selected tab was hardcoded to white)

#719 is related.

[extrawurst]

Thanks! closed via #723