feat: improve the readme.md

[xmfcx]

Description

This PR modernizes the repository's README and adds a missing .gitignore entry for Python virtual environments.

Changes

.gitignore

• Add /.venv/ to ignore Python virtual environment directories

README.md

• Redesigned with a centered logo, CI badge, and license badge
• Added a clear project description and link to live documentation
• Added a Getting started locally section with step-by-step setup instructions (clone → venv → install → serve)
• Expanded Contributing section with a note about reviewing guidelines before submitting a PR
• Added License section referencing Apache 2.0
• General copy and formatting improvements throughout

Motivation

The previous README lacked onboarding instructions, making it harder for new contributors to run the docs site locally. The updated README brings it in line with common open-source project conventions and reduces friction for first-time contributors.

Before & After

How was this PR tested?

• feat: improve the readme.md #776 (comment)

[github-actions]

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[github-actions]

Documentation URL: https://autowarefoundation.github.io/autoware-documentation/pr-776/
Modified URLs:

• https://autowarefoundation.github.io/autoware-documentation/pr-776/

[xmfcx]

This can be checked here: https://github.com/xmfcx/autoware-documentation/blob/4a71273a1d7dfb432455822e9a133b841b5a8feb/README.md

this is not part of the deploy docs mkdocs pipeline