Ignition -> Gazebo

[jennuine]

🦟 Bug fix

Part of:

• Increase test coverage gz-sim#1575
• Rename Ignition to Gazebo gazebo-tooling/release-tools#698

Summary

Updated links and naming in README.md

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov]

Codecov Report

Merging #674 (cff1b8f) into ign-rendering3 (81fb6d4) will not change coverage.
The diff coverage is n/a.

❗ Current head cff1b8f differs from pull request most recent head b6f51ae. Consider uploading reports for the commit b6f51ae to get more accurate results

@@               Coverage Diff               @@
##           ign-rendering3     #674   +/-   ##
===============================================
  Coverage           53.38%   53.38%           
===============================================
  Files                 131      131           
  Lines               12021    12021           
===============================================
  Hits                 6418     6418           
  Misses               5603     5603           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 81fb6d4...b6f51ae. Read the comment docs.