add Community Layouts for LAYOUT_(ansi|iso|default) keyboards

[dunk2k]

Description

Assign matching Community Layout(s) to keyboards with LAYOUT_(ansi|iso|default) macro

• where applicable; utilise layout_aliases to match layout name to Community Layout name
  • in keymaps, change layout macro names to match added Community Layout
• add matrix_diagram.md where accurate information available

Keyboard Specific

• ghs/jem:
  • move ISO layouts into soldered sub-directory, as hotswap_ansi doesn't support ISO layouts

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).

[dunk2k]

this PR segmented alphabetically into smaller PRs