GCP custom entity extractor added (AutoML)

[itsmasabdi]

Description

This is the implementation of GCP custom entity extraction for sequence labelling https://cloud.google.com/natural-language/automl/docs

Type of change

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

I has been tested locally and using a custom dataset that I have trained myself.

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] Any dependent changes have been merged and published in downstream modules