[Documentation] Add missing htmx:sendAbort event

[scrhartley]

Description

The event htmx:sendAbort is missing from the documentation. The related events htmx:sendError and htmx:timeout are there, but this one is missing.
Although htmx:xhr:abort is already documented. its detail data is different.

Testing

Tested locally using Zola to ensuring linking works correctly.

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

[Telroshan]

Good catch, thanks!