SPARKNLP-809: Add warning to ForZeroShot annotators

[DevinTDHa]

Description

This PR adds a warning to ZeroShot annotators. As the annotators loop through the provided labels, the more labels have, the longer the process will take.

Additionally

• added missing Annotator Entries on the main page
• Fixed some inconsistencies with the documentation of the DocumentAssembler, resolves DocumentAssembler on array<string> #13816.

Motivation and Context

How Has This Been Tested?

No Code Changes

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Code improvements with no or little impact
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING page.
• I have added tests to cover my changes.
• All new and existing tests passed.

[coveralls]

Pull Request Test Coverage Report for Build 5055186599

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage remained the same at 65.844%

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Files with Coverage Reduction	New Missed Lines	%
src/main/scala/com/johnsnowlabs/nlp/annotators/sentence_detector_dl/SentenceDetectorDLModel.scala	2	82.72%

Totals
Change from base Build 4945586143:	0.0%
Covered Lines:	8640
Relevant Lines:	13122

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💛 - Coveralls