Behaviour: Support Label type custom field#163

As a user, I want to have the ability to modify the value of the Labels custom field type using behaviour.

We use custom label fields extensively in my company. This would be super helpful

Update: We support the labels custom field in Create, Issue and Transition View.

To see all Behaviours supported fields, please check the following page in our documentation: https://docs.adaptavist.com/sr4jc/latest/features/behaviours/behaviours-supported-fields-and-products