HtmxAjaxHelperContext typedef should have all optional fields

[anentropic]

Description

The typedef is currently more strict than the code, and prevents IMHO the most useful way to configure ajax requests.

I also added a clarification to the htmx.ajax docs about what specifying source in the context object actually does.

See discussion here:
#2698

Testing

Please explain how you tested this change manually, and, if applicable, what new tests you added. If
you're making a change to just the website, you can omit this section.

Checklist

• I have read the contribution guidelines
• I have targeted this PR against the correct branch (master for website changes, dev for
  source changes)
  ...oh, do the docs and code changes need to be in separate PRs?
• 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]

do the docs and code changes need to be in separate PRs?

Since the code changes here only affect the JSDoc thus the "code's documentation" + it comes from the same source issue/discussion, I would say it's totally fine.

Though, could you please :

• remove the changes to the duplicated htmx scripts in www? Those are generated from src or dist when we publish a release
• remove the change to CONTRIBUTING.md? I think we'll do that in another PR as it's not directly related to the problem here

[anentropic]

do the docs and code changes need to be in separate PRs?

Since the code changes here only affect the JSDoc thus the "code's documentation" + it comes from the same source issue/discussion, I would say it's totally fine.

Though, could you please :

• remove the changes to the duplicated htmx scripts in www? Those are generated from src or dist when we publish a release
• remove the change to CONTRIBUTING.md? I think we'll do that in another PR as it's not directly related to the problem here

Thanks, have made those changes.