Add Problem matchers to surface failures prominently in the UI

[timtebeek]

It looks like / FAILED$/ might be a pattern to match things, or possibly />.* FAILED$/.

https://github.com/actions/toolkit/blob/main/docs/problem-matchers.md
n.b. the documentation is buggy, I thought I wrote a PR to fix it, but I can't find it 😞

Slack Message

[timtebeek]

Improved documentation here: https://github.com/actions/toolkit/pull/1414/files

[jsoref]

The /s above are to denote regular expressions. In the problem matcher syntax, you get to use Java style strings to represent regular expressions, which means using double-backslashes (\n => \\n) for builtin regular expression character classes (not applicable in the above example)

[timtebeek]

Might also help to highlight any build scans where available, such as for instance:

Publishing build scan...
https://ge.openrewrite.org/s/cpl5aclixmt5s

[jsoref]

Here's a random sample reporter which might help as reading material:
https://github.com/check-spelling/check-spelling/blob/e3b1f361ff1ff04c15a891c14438cf077a87ae8e/reporter-misc.json
And here's the glue to connect it to GitHub:
https://github.com/check-spelling/check-spelling/blob/e3b1f361ff1ff04c15a891c14438cf077a87ae8e/unknown-words.sh#L1567

A warning: if you're running things using GitHub Action's Docker support, you may be unhappy (I haven't checked, but I don't think you are)