feat(behaviors): Add caps word (&caps_word).

* Add new `&caps_word` behavior that acts like caps lock, but
  releases automatically when any "break" keycode is pressed.

docs/docs/behaviors/caps-word.md

@@ -0,0 +1,74 @@
+---
+title: Caps Word Behavior
+sidebar_label: Caps Word
+---
+
+## Summary
+
+The caps word behavior behaves similar to a caps lock, but will automatically deactivate when one of the configured "break keycodes" is pressed, or if the caps word key is pressed again. For smaller keyboards, using [mod-taps](/docs/behaviors/mod-tap), this can help avoid repeated alternating holds when typing words in all caps.
+
+The modifiers are applied only to to the alphabetic (`A` to `Z`) keycodes, to avoid automatically appliying them to numeric values, etc.
+
+### Behavior Binding
+
+- Reference: `&caps_word`
+
+Example:
+
+```
+&caps_word
+```
+
+### Configuration
+
+#### Continue List
+
+By default, the caps word will remain active when any alphanumeric character or the underscore (`UNDERSCORE`) characters are pressed. Any other keycode sent,
+will turn off caps word. If you would like to override this, you can set a new array of keys in the `continue-list` property in your keymap:
+
+```
+&caps_word {
+    continue-list = <UNDERSCORE MINUS>;
+};
+
+/ {
+    keymap {
+        ...
+    };
+};
+```
+
+#### Applied Modifier(s)
+
+In addition, if you would like _multiple_ modifiers, instead of just `MOD_LSFT`, you can override the `mods` property:
+
+```
+&caps_word {
+    mods = <MOD_LSFT | MOD_LALT>;
+};
+
+/ {
+    keymap {
+        ...
+    };
+};
+```
+
+### Multiple Caps Breaks
+
+If you want to use multiple caps breaks with different codes to break the caps, you can add additional caps words instances to use in your keymap:
+
+```
+/ {
+    prog_caps: behavior_prog_caps_word {
+        compatible = "zmk,behavior-caps-word";
+        label = "PROG_CAPS";
+        #binding-cells = <0>;
+        continue-list = <UNDERSCORE>;
+    };
+
+    keymap {
+        ...
+    };
+};
+```

docs/sidebars.js

@@ -27,6 +27,7 @@ module.exports = {
       "behaviors/mod-morph",
       "behaviors/sticky-key",
       "behaviors/sticky-layer",
+      "behaviors/caps-word",
       "behaviors/reset",
       "behaviors/bluetooth",
       "behaviors/outputs",