[Keymap] Add vitoni keymap for GMMK Pro (ISO) (#15006)

* [Keymap] Add vitoni layout for GMMK Pro (ISO)

Keymap has layered cursor keys similar to laptop keyboards.

* Configure RGB defaults for startup

* Configure encoder to change value/brightness on FN layer

* Remove FN layer and add dedicated RGB layer

* Make RGB layer sticky (using TG) to avoid holding FN while configuring RGB

* Add RGB indicators for active layers

* Add RGB indicator for active RESET mode

Signed-off-by: Victor Toni <victor.toni@gmail.com>

* Configure idle / USB suspend settings

* Add RGB fade in when resuming after suspend

* Add RGB fade out before suspend

* Add fade out before idle

* Add breathe effect when idle

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diff --git a/keyboards/gmmk/pro/iso/keymaps/vitoni/readme.adoc b/keyboards/gmmk/pro/iso/keymaps/vitoni/readme.adoc
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+= ViToni's keymap for GMMK Pro ISO
+
+== Layout
+Based on the stock layout but making use of CAPS as FN similar to laptop keyboards.
+This frees up the left row for other uses (although not remapped yet).
+Since both Delete and Insert are used for coding they are part of the CAPS layer as well.
+
+The differences are as follows:
+
+=== Layer 0 (`_BASE`)
+Mostly stock + CAPS goes to layer `_MOV`.
+FN toggles the layer `_RGB`.
+
+=== Layer 1 (`_MOV`), accessed by pressing `CAPS` on layer `_BASE`
+[%header]
+|===
+| Key / Action          | Mapped to
+| ESC                   | _RESET_
+| F1                    | KC_MYCM
+| F2                    | KC_WHOM
+| F3                    | KC_CALC
+| F4                    | KC_MSEL
+| F5                    | KC_MPRV
+| F6                    | KC_MPLY
+| F7                    | KC_MSTP
+| F8                    | KC_MNXT
+| F9                    | KC_MUTE
+| F10                   | KC_VOLD
+| F11                   | KC_VOLU
+| N                     | NK_TOGG
+| Delete                | Insert
+| Left                  | Home
+| Right                 | End
+| Up                    | PgUp
+| Down                  | PgDn
+|===
+
+=== Layer 2 (`_RGB`), accessed by pressing `FN` on layer `_BASE`
+Revamped the stock FN layer to focus on RGB only.
+
+[%header]
+|===
+| Key / Action          | Mapped to
+| Knob clockwise        | Value/Brightness up
+| Knob anti-clockwise   | Value/Brightness down
+| Backspace             | _RESET_
+| Enter                 | RGB_TOG
+| Del                   | RGB_MOD
+| PgUp                  | RGB_RMOD
+| PgDn                  | RGB_SPI
+| End                   | RGB_SPD
+| Left                  | RGB_HUD
+| Right                 | RGB_HUI
+| Up                    | RGB_SAI
+| Down                  | RGB_SAD
+|===
+
+No other changes have been made.
+
+== RGB light
+
+The code customizing RGB light usage is decribed here:
+
+* link:../../../../../../users/vitoni/readme.adoc[/users/vitoni/readme.adoc]
+
+When using  `RGB_DISABLE_TIMEOUT` addtional options are available:
+
+* `RGB_FADE_IN` makes the RGB lights fade in instead of setting the value/brightness to 100% (implicitly due to HSV including the brightness) when resuming after RGB lights have been turned off.
+Fade in occurs when the keyboard is initialized and when the RGB brightness has been changed (e.g. suspending, fade out, etc.).
+* `RGB_DISABLE_WITH_FADE_OUT` activates fade out before the keyboard is disabled by `RGB_DISABLE_TIMEOUT`.
+
+Parameters used to define the behavior are:
+[%header]
+|===
+|Key | Default | Description
+
+| RGB_MATRIX_MAXIMUM_BRIGHTNESS
+| 200 (<= UNIT8_MAX)
+| Maximum assumed value for brightness.
+Used to calculate lead time for fade out before suspend timeout.
+
+|===
+
+`RGB_IDLE_TIMEOUT` enables fading out after being idle for the defined time and allows
+* `RGB_IDLE_BREATHE` also activates a brethe effect while idling.
+
+[%header]
+|===
+|Key | Default | Description
+
+|RGB_IDLE_TIMEOUT
+|4500
+|Time in milliseconds without activity before considered to be idle.
+
+|RGB_IDLE_MINIMUM_BRIGHTNESS
+|`RGB_MATRIX_MAXIMUM_BRIGHTNESS` / 5
+|Brightness value RGB is dimmed to when starting to idle. +
+When breathing used as the lower bound of the brightness value.
+
+|RGB_IDLE_MAXIMUM_BRIGHTNESS
+|`RGB_MATRIX_MAXIMUM_BRIGHTNESS` * 2/5
+|Upper bound of brightness value of the RGB light while breathing.
+
+|===