* feat(icons): added letter icons for each uppercase letter of the English alphabet
* feat(icons): extend letter icons with specific use cases instead of generic ones
* feat(icons): replaced letter-z with more grid-aliged version
* feat(icons): add contributors from strikethrough to letter-s
* feat(icons): added square-letter-* & circle-letter-* icons
* feat(icons): manually optimized some icons
* fix(icons): deprecated circle-parking
* Rename import
* fix(icons): fix use case syntax for (circle|square)-letter icons
* fix(icons): added new Letters & digits category
* fix(icons): added numbers to new Letters & digits category
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Co-authored-by: Eric <eric.fennis@gmail.com>