Create a Vale rule that promtps a user about merge conflict markers

[dfitzmau]

Describe the bug
A recent PR was merged that included a missed merge conflict marker: openshift/openshift-docs#74760

Examples:

• <<<<<<< triggers a merge conflict marker vale alert.
• >>>>>>> triggers a merge conflict marker vale alert.
• ======= triggers a merge conflict marker vale alert.

These marker examples represent how GitHub flags a merge conflict location in a document.

To Reproduce
Steps to reproduce the behavior:

1.Doc includes <<<<<<< HEAD
2. Vale reports an illegitimate alert: error

Expected behavior
A clear and concise description of what you expected to happen.

Additional context
As per the GH docs, <<<<<<< HEAD is the offical syntax for the opening merge conflict marker.

Running grep --include=*.adoc -rnw . -e ">>>>>>>" against the openshift-docs repo show no results. Likewise with the reverse arrows. The equal signs could cause conflict so the regex restriction is important (7 x =).

[bergerhoffer]

Although I agree this is a good idea, we'd have to be careful what we check for, otherwise it will hit on things that are valid. For example, ======= can be valid AsciiDoc. Some people use more equal signs than necessary for table openings/closing, etc. Or could be regular code output.

At the very least, I believe <<<<<<< HEAD would be safe to check for. I'm less sure about whether >>>>>>> would also be safe, or if it's possible that could be a legitimate entry. Maybe they'd have to be warnings to be safe.

[dfitzmau]

PR openshift/openshift-docs#74760 merged. Closing this issue.

[dfitzmau]

Test PR on docs-openshift repository: openshift/openshift-docs#74936