Improve GitHub error highlighting

[jsoref]

Short description

As an occasional developer, it's really frustrating to find the lines in the build output that are real errors. By using a problem-matcher, we can surface them for people.

Additional patterns can be added later to match other cases.

Testing is partially here: https://github.com/check-spelling-sandbox/pdns/actions/runs/19764066930

Checklist

I have:

• [x] read the CONTRIBUTING.md document
• [x] read and accepted the Developer Certificate of Origin document, including the AI Policy, and added a "Signed-off-by" to my commits
• [x] compiled this code
• [x] tested this code
• [ ] included documentation (including possible behaviour changes)
• [ ] documented the code
• [ ] added or modified regression test(s)
• [ ] added or modified unit test(s)
• [ ] checked that this code was merged to master

[coveralls]

Pull Request Test Coverage Report for Build 19765062687

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 33 unchanged lines in 13 files lost coverage.
• Overall coverage increased (+0.03%) to 73.135%

---

Files with Coverage Reduction	New Missed Lines	%
pdns/dnsdistdist/dnsdist-tcp.cc	1	77.75%
pdns/misc.cc	1	62.07%
pdns/validate.cc	1	68.54%
pdns/recursordist/rec-eventtrace.hh	2	58.41%
pdns/recursordist/rec-main.cc	2	64.79%
pdns/recursordist/rec-tcpout.cc	2	79.53%
pdns/recursordist/sortlist.cc	2	74.12%
modules/gpgsqlbackend/spgsql.cc	3	67.94%
pdns/axfr-retriever.cc	3	67.34%
pdns/packethandler.cc	3	72.59%
<!--	Total:	33

Totals
Change from base Build 19741851688:	0.03%
Covered Lines:	128155
Relevant Lines:	164534

---

💛 - Coveralls