Add repo specific issue templates

[azeey]

Summary

(Related to gazebosim/gz-sim#1461)

Override the org level issue templates in order to make the issue templates more specific to this repo. This is currently just a copy of the files from https://github.com/ignitionrobotics/.github, but we are planning to remove the GUI/Rendering section from the issue templates there.

Note, I had to copy both files in ISSUE_TEMPLATES even though we only need to override bug_report.md because Github will not use the org level defaults if it finds any files in the repo's ISSUE_TEMPLATES directory.

Test it

Checklist

• Signed all commits for DCO
• Added tests
• Added example and/or tutorial
• 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 #616 (b5b2e37) into ign-rendering6 (2abe4fb) will not change coverage.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           ign-rendering6     #616   +/-   ##
===============================================
  Coverage           80.00%   80.00%           
===============================================
  Files                   1        1           
  Lines                  15       15           
===============================================
  Hits                   12       12           
  Misses                  3        3           

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