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

Enhanced GitHub Actions CI for ultralytics/mkdocs repository with automated link checks and status badge addition.

📊 Key Changes

• 🔄 Updated the .github/workflows/format.yml file to include a links: true option.
• 🔑 Added token: ${{ secrets.GITHUB_TOKEN }} to allow necessary permissions for GitHub Actions.
• 📈 Included a new status badge in the README.md for visual tracking of format workflow.

🎯 Purpose & Impact

• 🚀 The links: true option aims to automatically validate hyperlinks, ensuring all links in documentation are functional.
• 🛡️ The GITHUB_TOKEN addition provides secure automated access for formatting action.
• 🌐 The README status badge offers immediate visibility of the workflow's health, enhancing transparency and trust for users.
• 💡 Potential impact includes smoother CI processes, improved documentation reliability, and up-to-date feedback on code quality for contributors and users.