Add a Getting Started and improve documentation

[RyanLua]

Description

This pull request includes several changes focused on improving the documentation and streamlining the codebase for the InstaWebhooks project. The most important changes include updates to the documentation, enhancements to the CI workflow, and refactoring of the argument parser.

Related Issues

Changes Made

Documentation improvements:

• Added a new "Getting Started" guide in docs/source/getting-started.rst to help users set up InstaWebhooks from scratch.
• Updated docs/source/conf.py to include new Sphinx extensions and footer icons for GitHub and Read the Docs. [1] [2]
• Added new features and customization options to the docs/source/index.rst and updated the table of contents. [1] [2]
• Refined the docs/source/usage.rst to provide clear examples and improved the reference section using argparse directive. [1] [2]

CI workflow enhancements:

• Modified the .github/workflows/ci.yml to include sparse checkout for the src directory and added sphinx-lint to the dependencies and linting steps. [1] [2] [3]

Codebase refactoring:

• Extracted the argument parser logic into a new src/instawebhooks/parser.py file and imported it in src/instawebhooks/__main__.py to improve modularity. [1] [2] [3] [4]

Other changes:

• Removed the onAutoForward attribute from the port configuration in .devcontainer/devcontainer.json.
• Added a new task in .vscode/tasks.json for building the documentation using sphinx-autobuild.

These changes collectively enhance the project's documentation, improve the CI workflow, and make the codebase more modular and maintainable.

Checklist

• I have tested these changes thoroughly.
• I have reviewed my code for any potential errors or issues.
• I have followed the code style guidelines for this project.

Additional Notes

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

OpenSSF Scorecard

Package	Version	Score	Details

Scanned Files

Copilot reviewed 9 out of 15 changed files in this pull request and generated no comments.

Files not reviewed (6)

• .devcontainer/devcontainer.json: Language not supported
• .vscode/tasks.json: Language not supported
• docs/source/_static/.gitkeep: Language not supported
• docs/source/getting-started.rst: Language not supported
• docs/source/index.rst: Language not supported
• docs/source/usage.rst: Language not supported