[ign-physics1] Workflow updates

[chapulina]

• Add labeler workflow
• Add triage workflow
• Add Ubuntu CI workflow with Codecov upload
• Update codecov badge

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (ign-physics1@520f6f0). Click here to learn what that means.
The diff coverage is n/a.

@@               Coverage Diff               @@
##             ign-physics1      #51   +/-   ##
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  Coverage                ?   82.71%           
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  Files                   ?       75           
  Lines                   ?     2389           
  Branches                ?        0           
===============================================
  Hits                    ?     1976           
  Misses                  ?      413           
  Partials                ?        0           

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