Use README vendor build badges

[DRSDavidSoft]

Summary

• Dynamically read each vendor repository README through the GitHub API.
• Parse Markdown badge links and select the best build/status/CI badge from the README.
• Use — when the vendor README has no build/status badge, instead of inventing one.
• Keep the four-column table: Name, Old Version, New Version, Build Status.

Badge comparison from current vendors

• git-for-windows/git

  • Official README badge: https://github.com/git-for-windows/git/workflows/CI/badge.svg
  • Previous generated badge: https://img.shields.io/github/check-runs/git-for-windows/git/<tag>?label=build
  • Difference: official badge is GitHub workflow CI, not a Shields check-runs badge for a tag.

• chrisant996/clink

  • Official README badge: none found.
  • Previous generated badge: https://img.shields.io/github/check-runs/chrisant996/clink/<tag>?label=build
  • Difference: we were inventing a status badge that upstream does not publish in README; now the cell is —.

• microsoft/terminal

  • Official README badge: https://dev.azure.com/shine-oss/terminal/_apis/build/status%2FTerminal%20CI?branchName=main
  • Previous generated badge: https://img.shields.io/github/check-runs/microsoft/terminal/<tag>?label=build
  • Difference: official badge is Azure DevOps Terminal CI, not GitHub check-runs.

• vladimir-kotikov/clink-completions

  • Official README badge: https://github.com/vladimir-kotikov/clink-completions/actions/workflows/code-check.yml/badge.svg?branch=master
  • Previous generated badge: https://img.shields.io/github/check-runs/vladimir-kotikov/clink-completions/<tag>?label=build
  • Difference: official badge is the code-check.yml workflow badge for master, not a generic Shields check-runs badge for a tag.

Validation

• git diff --check
• Updated ⬆️ Update 4 vendored dependencies #3093 live from this branch and verified the body contains the three README badges, — for clink, and no generated check-runs or release-version shields.