Enforcing YAML Schemas

[merijjeyn]

Enforce YAML schemas like the CV schema here: https://github.com/rendercv/rendercv/blob/main/schema.json

So when trying to add a field to an object, you could check the possible child types of the object and show those as option only

[maliknajjar]

this is a very useful feature that I thought of implementing from the beginning
Im working on creating the version 2.0 of guifier and I will for sure add this suggested feature