Use app header color as default selected tab color + allow styling

[spacegaier]

Breaking change

Proposed change

In the default theme, the issue is not visible, since the colors match "by accident". But this PR now ensures that if the user specified a dedicated header text color via --app-header-text-color the same one is used to mark the currently active tab by default. On top I added a variable --app-header-selection-bar-color so themes can adjust the color.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes Default --paper-tabs-selection-bar-color to --app-header-text-color #7946
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io