Docs/add more documentation

[anandan947]

Description

This PR adds more documentation to the Docs.

• How to build a simple chatbot with Legion
• How tools work in Legion

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Performance improvement
• Code cleanup or refactor

Implementation Details

This contains the following addition to the Docs -

• Adds a chatbot example since many that is likely to be many people's first use-case that they want to try out.
• Adds explanation of what tools do and how they work
• Adds explanation of how to do parameter injection with tools.
• Adds loading the .env file for setting the API keys in the quickstart example.

Testing

• All existing tests pass
• Added new tests for the changes

Documentation Changes

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes