Prepare for 13.6.0 Release

[azeey]

🎈 Release

Preparation for 13.6.0 release.

Comparison to 13.5.0: sdformat13_13.5.0...sdf13

Needed by <PR(s)>

Checklist

• Asked team if this is a good time for a release
• There are no changes to be ported from the previous major version
• No PRs targeted at this major version are close to getting in
• Bumped minor for new features, patch for bug fixes
• Updated changelog
• Updated migration guide (as needed)
• Link to PR updating dependency versions in appropriate repository in gazebo-release (as needed):

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.

[scpeters]

I think #1292 should be added to the changelog

[scpeters]

I think #1292 should be added to the changelog

b553b01

[codecov]

Codecov Report

Merging #1315 (b71343f) into sdf13 (9f7a377) will not change coverage.
The diff coverage is n/a.

❗ Current head b71343f differs from pull request most recent head b553b01. Consider uploading reports for the commit b553b01 to get more accurate results

@@           Coverage Diff           @@
##            sdf13    #1315   +/-   ##
=======================================
  Coverage   87.58%   87.58%           
=======================================
  Files         128      128           
  Lines       17090    17090           
=======================================
  Hits        14968    14968           
  Misses       2122     2122