feat(docs): add langchain and cohere overview

[gautamgambhir97]

Proposed Changes

Add langchain and cohere overview

Linked Issues

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Types of changes

What type of change does this pull request make (put an x in the boxes that apply)?

• Content update.
• Bug fix (non-breaking change that fixes an issue).
• New feature added (non-breaking change that adds functionality).
• Breaking change (fix or feature that would cause existing functionality to stop working as expected).
• Something else (e.g., tests, scripts, example, deployment, infrastructure).

Checklist

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• I have read the CONTRIBUTING guide
• Checks and tests pass locally

Further comments

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