Wilba Tech WT75-A Layout Additions and Touch-Up (qmk#20877)

* add matrix_diagram.md

* info.json: apply friendly formatting

* rename LAYOUT_all to LAYOUT_ansi_blocker_split_bs

* add LAYOUT_ansi_blocker

* add LAYOUT_ansi_blocker_tsangan_split_bs

* add LAYOUT_ansi_blocker_tsangan

* readme.md: update metadata section

- convert to list
- update maintainer username