Update Actions with Lychee and GitHub Token

[pderrenger]

This pull request adds an improved Ultralytics Actions workflow to automatically format code and documentation to the new Ultralytics official standards maintained at https://github.com/ultralytics/actions.

Five individual actions are run by default now including a new broken links check for markdown and HTML files. Disable individual actions by setting them to false or removing their line, i.e. delete 'markdown: true' line to disable markdown formatting.

To customize an action use a pyproject.toml file in this repo. For details see https://github.com/ultralytics/actions.

# Ultralytics 🚀 - AGPL-3.0 license
# Ultralytics Actions https://github.com/ultralytics/actions
# This workflow automatically formats code and documentation in PRs to official Ultralytics standards

name: Ultralytics Actions

on:
  push:
    branches: [main]
  pull_request_target:
    branches: [main]

jobs:
  format:
    runs-on: ubuntu-latest
    steps:
      - name: Run Ultralytics Formatting
        uses: ultralytics/actions@main
        with:
          token: ${{ secrets.GITHUB_TOKEN }}  # automatically generated
          python: true
          docstrings: true
          markdown: true
          spelling: true
          links: true

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhancements to GitHub workflows and repository documentation have been introduced in this PR for Ultralytics WAVE.

📊 Key Changes

• Changed GitHub Actions trigger from pull_request to pull_request_target.
• Added automated link checking to the formatting workflow.
• Inserted a status badge for Ultralytics formatting actions in the README.
• Adjusted the indentation in the Python package list in the README for improved readability.

🎯 Purpose & Impact

• Changing the trigger to pull_request_target allows workflow runs to execute with write permissions, which can be useful for automating certain repository management tasks securely 🔒.
• Checking links as part of the CI ensures that all hyperlinks in documentation are valid and not broken, enhancing the quality and reliability of the repository's documentation 🔗.
• The inclusion of a status badge provides a quick visual indication of the health of the codebase regarding code style and formatting, promoting transparency and credibility 👀.
• Improved indentation in documentation aids in reader comprehension and presents a cleaner, more professional appearance of the setup instructions ✅.

These improvements collectively enhance the workflow automation, maintain the integrity of the documentation, and assist both contributors and users in engaging more effectively with the repository.