Persistence of a custom lock is disabled by default, but it can now
be enabled in the dts keyboard config similar to this:
```
deadlock: deadlock {
compatible = "zmk,behavior-custom-lock";
label = "dead-key-toggle";
#binding-cells = <0>;
persistence = "enabled";
}
```
Currently the options are `disabled`, `enabled` and `per-profile`, where
the latter doesn't do anything different to `enabled` as of right now.
Signed-off-by: Sophie Tyalie <dev@flowerpot.me>
cac33f493a