add 75_(ansi|iso) Community Layouts to mechlovin/olly/octagon

[dunk2k]

Description

• add 75_ansi and 75_iso Community Layouts
• add additional layouts
• add matrix_diagram.md file
• rename LAYOUT_split_bs to LAYOUT_all
  • layout_aliases changed to match

cc: @mechlovin

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• n/a

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[github-actions]

Thank you for your contribution!
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[dunk2k]

Please label as awaiting review