In the case where you don't need anything special from your GObject
property getters and setters, just correct handling of notify signals
and default values, it's now possible to leave out the getters and
setters, and GJS will just do the right thing. This is convenient for
JS code authors as well as avoiding problems caused by missing getters
and setters.

This only works for read-write properties. If a read-only or write-only
property is missing its accessor, then one is generated which throws.

If the property name consists of multiple words, then accessors will be
generated for all three variants: kebab-case, snake_case, and camelCase.
Additionally, if you do provide accessors for one of these, then they
will be copied to the other two variants.

See: #306