Update our triage docs for new tag

[theunrepentantgeek]

What this PR does / why we need it:

We're introducing the tag needs-triage and a bot to automatically apply it to new issues; this PR updates our docs on what we're looking at when we triage.

How does this PR make you feel:

If applicable:

• this PR contains documentation

[codecov-commenter]

Codecov Report

Merging #1681 (4c3700a) into master (a8e30ae) will not change coverage.
The diff coverage is n/a.

❗ Current head 4c3700a differs from pull request most recent head 6cf4a9b. Consider uploading reports for the commit 6cf4a9b to get more accurate results

@@           Coverage Diff           @@
##           master    #1681   +/-   ##
=======================================
  Coverage   67.98%   67.98%           
=======================================
  Files         212      212           
  Lines       15151    15151           
=======================================
  Hits        10300    10300           
  Misses       4082     4082           
  Partials      769      769           

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