fix: render border colors in Avatar with placeholder initials

[adamgruber]

Description

This PR fixes an issue with the Avatar component where the color prop is ignored when using placeholder initials.

Partially Fixes #451

Type of change

• Bug fix (non-breaking change which fixes an issue)

Breaking changes

None

How Has This Been Tested?

• Added a new unit test to verify expected classnames are applied in the appropriate scenario

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (main@89d2ff8). Click here to learn what that means.
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #521   +/-   ##
=======================================
  Coverage        ?   98.96%           
=======================================
  Files           ?      127           
  Lines           ?     5530           
  Branches        ?      465           
=======================================
  Hits            ?     5473           
  Misses          ?       57           
  Partials        ?        0           

Impacted Files	Coverage Δ
src/lib/components/Avatar/Avatar.tsx	98.55% <100.00%> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[adamgruber]

Thanks for merging! Any idea when this change will be released?

[rluders]

@adamgruber I think the next release will be the 0.4.0, which should be done when #443 and #465 is done. You can help to finish this task as well, I have a PR pending for review #500 and we have some other components that need to allow per-component theme overwriting.