Add option to define refs in issue templates

[qwerty287]

Adds a markdown header option ref that allows you to set the ref the issue should belong.

[codecov-commenter]

Codecov Report

Merging #17842 (cc3a227) into main (a6d4a85) will decrease coverage by 0.00%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##             main   #17842      +/-   ##
==========================================
- Coverage   45.26%   45.26%   -0.01%     
==========================================
  Files         820      820              
  Lines       91064    91067       +3     
==========================================
- Hits        41218    41217       -1     
- Misses      43284    43287       +3     
- Partials     6562     6563       +1     

Impacted Files	Coverage Δ
modules/structs/issue.go	0.00% <ø> (ø)
routers/web/repo/issue.go	38.92% <33.33%> (-0.01%)	⬇️
modules/charset/charset.go	71.71% <0.00%> (-4.05%)	⬇️
modules/queue/workerpool.go	50.76% <0.00%> (-1.53%)	⬇️
services/pull/pull.go	41.70% <0.00%> (ø)
models/repo_list.go	84.01% <0.00%> (+0.81%)	⬆️
modules/process/manager.go	82.94% <0.00%> (+1.55%)	⬆️
models/unit/unit.go	43.83% <0.00%> (+2.73%)	⬆️

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[zeripath]

make lgtm work