[Core] Allow customizing PWM frequency (#21717)

* [Core] Allow customizing PWM frequency

Some frequencies can cause audible noise. Changing the frequency
eliminates that.

Signed-off-by: Daniel Schaefer <dhs@frame.work>

* docs/feature-backlight: Mention PWM frequency

Signed-off-by: Daniel Schaefer <dhs@frame.work>

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Signed-off-by: Daniel Schaefer <dhs@frame.work>

Merge remote-tracking branch 'origin/master' into develop

Added kiserdesigns keyboard folder and Madeline keyboard (#21857)

Co-authored-by: Drashna Jaelre <drashna@live.com>
Co-authored-by: Ryan <fauxpark@gmail.com>

Merge remote-tracking branch 'origin/master' into develop

Add M6-C Keyboard Firmware (#21852)

Co-authored-by: Joel Challis <git@zvecr.com>
Co-authored-by: Drashna Jaelre <drashna@live.com>
Co-authored-by: Wolf <contact@vwolf.be>

Merge remote-tracking branch 'origin/master' into develop

[keyboard] add redragon/k667 (#21417)

Co-authored-by: Duncan Sutherland <dunk2k_2000@hotmail.com>
Co-authored-by: jack <0x6a73@protonmail.com>
Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: syc <squall_sha@163.com>

Merge remote-tracking branch 'origin/master' into develop

Add 1upkeyboards Super16v3 (#21665)

Co-authored-by: Duncan Sutherland <dunk2k_2000@hotmail.com>

Remove old `IS_LED_ON/OFF()` macros (#21878)

Merge remote-tracking branch 'origin/master' into develop

chore: ignore virtual environment directory (#20905)

Merge remote-tracking branch 'origin/master' into develop

nullbitsco/snap: fix broken keymaps (#21877)

Merge remote-tracking branch 'origin/master' into develop

AH Haven65 Community Layout support (#21880)

* [refactor] rename LAYOUT to LAYOUT_65_ansi_blocker

* [enhancement] enable Community Layout support

Merge remote-tracking branch 'origin/master' into develop

Abko AK84BT Layout Touch-Up (#21876)

* [refactor] rename LAYOUT_75_ansi to LAYOUT

* [enhancement] touch-up layout

1UpKeyboards Pi60 Layout Additions (#21874)

* [refactor] rename LAYOUT_60_ansi to LAYOUT_all

* [enhancement] add LAYOUT_60_ansi

* [enhancement] add LAYOUT_60_ansi_split_bs_rshift

* [enhancement] add LAYOUT_60_ansi_tsangan

* [enhancement] add LAYOUT_60_tsangan_hhkb

* [enhancement] add LAYOUT_60_iso

* [enhancement] add LAYOUT_60_iso_split_bs_rshift

* [enhancement] add LAYOUT_60_iso_tsangan

* [enhancement] add LAYOUT_60_iso_tsangan_split_bs_rshift

* [enhancement] enable Community Layout support

* [enhancement] add LAYOUT_60_hhkb

* [enhancement] add LAYOUT_60_ansi_arrow

* [enhancement] add LAYOUT_60_iso_arrow

* [docs] add layout/matrix diagram

Merge remote-tracking branch 'origin/master' into develop