Add subscript to issue templates

[opentelemetrybot]

Adds a subscript to issue templates to provide guidance for end-users and others to interact with issues in a measurable way. This follows recommendations outlined in the maintainer guide for managing popular issues.

cc @danielgblanco

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.1%. Comparing base (42139cb) to head (8609cd4).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3094   +/-   ##
=====================================
  Coverage   80.1%   80.1%           
=====================================
  Files        126     126           
  Lines      21957   21957           
=====================================
+ Hits       17603   17604    +1     
+ Misses      4354    4353    -1     

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