docs: add contributor notes about running unit tests.

[pwhelan]

Add some notes for contributors for running unit tests.

This is related to issue #5716.

---

Enter [N/A] in the box, if an item is not applicable to your change.

Testing Before we can approve your change; please submit the following in a comment:

• [N/A] Example configuration file for the change
• [N/A] Debug log output from testing the change

• [N/A] Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• [N/A] Attached local packaging test output showing all targets (including any new ones) build.

Documentation

• [N/A] Documentation required for this feature

Backporting

• [?] Backport to latest stable release.

---

Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[patrick-stephens]

https://github.com/DavidAnson/markdownlint/blob/v0.26.1/doc/Rules.md#md014---dollar-signs-used-before-commands-without-showing-output

A dollar sign before a command is not needed if there is not an output of the command.

See also: #2045

Yeah I noticed that @nokute78 although we should really catch this in CI linting so it is clear and objective. I think it is currently inconsistent so we should improve it.

[patrick-stephens]

@pwhelan @nokute78 could we get this merged?

[nokute78]

I agree.

@patrick-stephens Any update for CI linting ?

[patrick-stephens]

I agree.

@patrick-stephens Any update for CI linting ?

None yet, I don't think it should block this PR. I'll discuss to see what people want to do as it'll likely flag a lot of the current docs.

[github-actions[bot]]

This PR is stale because it has been open 45 days with no activity. Remove stale label or comment or this will be closed in 10 days.

[patrick-stephens]

@pwhelan shall we get this merged?