Groovy Hook Scripts page: Clarify allowed HOOK values

[MarkEWaite]

Problem with the Groovy Hook Scripts page, source file

A user reported to the "Jenkins User Documentation - Page and Content Feedback" form that

It wasn't immediately clear that HOOK.groovy.d really meant one of 'init.groovy.d' or 'boot-failure.groovy.d'

The section ""Post initialization script (init hook)"" gives that as an example, but I'll admit I didn't read that far (and thought I could name the directories literally HOOK.groovy.d)

Possible Solution

The submitter also offered a suggestion for a possible solution:

So right where the bullet list ""The following events use this mechanism:"" is, maybe make it crystal clear that 'HOOK"" must be replaced with one of the following types.