Steno combinedkeys

[freqmod]

Description

Makes it possible to press one key instead of trying to hit multiple keys with one finger when inputting steno graphical chords on a keyboard. For example see the second row in the keymap below, combining the key on the keyboard row above and below into one key.

Example layer (for planck) using the combined consonant keys.
`[0] = LAYOUT_ortho_4x12(
STN_FN, STN_S1, STN_TL, STN_PL, STN_HL, STN_ST1, STN_ST3, STN_FR, STN_PR, STN_LR, STN_TR, STN_DR ,
STN_FN, STN_S3, STN_TKL, STN_PWL, STN_HRL, STN_ST1, STN_ST3, STN_FRR, STN_PBR, STN_LGR, STN_TSR, STN_DZR ,
XXXXXXX, STN_S2, STN_KL, STN_WL, STN_RL, STN_ST2, STN_ST4, STN_RR, STN_BR, STN_GR, STN_SR, STN_ZR ,
TG(10), ST_BOLT, ST_GEM, STN_NA, STN_A, STN_O, STN_E, STN_U, STN_NB, STN_PWR, STN_RE1, STN_RE2),

};`

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

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 tried to find some steno tests to extend, but i couldn't find any.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[stale]

Thank you for your contribution!
This pull request has been automatically marked as stale because it has not had activity in the last 45 days. It will be closed in 30 days if no further activity occurs. Please feel free to give a status update now, or re-open when it's ready.
For maintainers: Please label with awaiting review, breaking_change, in progress, or on hold to prevent the issue from being re-flagged.