docs: added local setup readme

[Ragini-Microsoft]

Purpose

This pull request enhances the documentation to better support both Azure deployment and local development workflows. The most significant updates are the addition of a dedicated local development setup guide and improved navigation for installation instructions. There is also a minor formatting change in a sample configuration file.

Documentation improvements:

• Updated the README.md to clearly separate Azure deployment instructions from local development, and added links to a new comprehensive local development setup guide covering Windows, WSL2, and cross-platform tools.
• Added a section to documents/DeploymentGuide.md directing users to the local development setup guide for running the application locally.

Configuration file formatting:

• Minor formatting adjustment in src/api/dotnet/appsettings.json.sample by adding a trailing comma for consistency.

Does this introduce a breaking change?

• Yes
• No

Golden Path Validation

• I have tested the primary workflows (the "golden path") to ensure they function correctly without errors.

Deployment Validation

• I have validated the deployment process successfully and all services are running as expected with this change.

What to Check

Verify that the following are valid

• ...

Other Information