Improve detail.elt event documentation

[MichaelWest22]

Description

Event documentation for detail.elt is incorrect and confusing as the current documentation has this field listed as the element that dispatched the request when in fact a different element is being passed into the event. The detail.elt is always the element that the event is triggered on in htmx and this has to often be the element in question and not the one that started the request.

Corresponding issue:
#3000

Testing

No testing just careful reading of source to check how the events are actually triggered

Checklist

• I have read the contribution guidelines
• I have targeted this PR against the correct branch (master for website changes, dev for
  source changes)
• This is either a bugfix, a documentation update, or a new feature that has been explicitly
  approved via an issue
• I ran the test suite locally (npm run test) and verified that it succeeded

[alexpetros]

Hey thanks for taking the time to do this, it's a really huge improvement!