Refactor the grammer so that we can support highlighting of model keyword and model identifier

[pantharshit00]

Right now grammar is laid out in a way that it is quite hard to highlight model <identifier> part.

Plugin needs some refactoring in order to highlight these fields properly. Kinda same goes for datamodel, enum

Example of the problem:

[pantharshit00]

Notice model Block is not highlighted in the above image