feat: allow using initials as Avatar placeholder

[iamargentum]

Refs: #357

Description

This PR adds a new prop, placeholderInitials, to the Avatar component. String passed in this prop will be displayed as Avatar's placeholder, if image is not provided.

Fixes #357

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change contains documentation update

Breaking changes

No breaking changes

How Has This Been Tested?

Just checked visually

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

Screencast.from.10-10-22.01.57.39.AM.IST.webm

[codecov]

Codecov Report

Base: 98.61% // Head: 98.59% // Decreases project coverage by -0.01% ⚠️

Coverage data is based on head (744042e) compared to base (6f6a63a).
Patch coverage: 94.44% of modified lines in pull request are covered.

❗ Current head 744042e differs from pull request most recent head 922eb83. Consider uploading reports for the commit 922eb83 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #375      +/-   ##
==========================================
- Coverage   98.61%   98.59%   -0.02%     
==========================================
  Files          89       89              
  Lines        4116     4138      +22     
  Branches      375      377       +2     
==========================================
+ Hits         4059     4080      +21     
- Misses         57       58       +1     

Impacted Files	Coverage Δ
src/lib/components/Avatar/index.tsx	98.05% <92.85%> (-0.82%)	⬇️
src/lib/theme/default.ts	100.00% <100.00%> (ø)
src/lib/components/Button/index.tsx	100.00% <0.00%> (ø)

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[rluders]

Thanks.

[rluders]

@iamargentum I guess that now the CI is just saying that we need to put some unit test to cover the new logic. :)

[iamargentum]

okay!
I've never really written a test though
i'll try to replicate what existing tests do, for the new logic