handle custom element manual input value collection

[MichaelWest22]

Description

Fix: FACE value not sent when used as standalone trigger (no form)

Form-associated custom elements (e.g. ) used as standalone htmx triggers outside a

stopped sending their value in beta4. This was a regression introduced by f02a86b ("Improve Non form input and checkbox handling").

The fix adds a single else if branch in __addInputValues for elements whose tag name contains a hyphen (the W3C-mandated marker for all custom elements). These are routed through the existing loop the same way BUTTON is — inputs = [elt] — so they pick up the name/disabled/included guards and fall through to formData.append(input.name, input.value) without any duplicated logic.

The form path (new FormData(form)) is unaffected and continues to collect FACE values via setFormValue as before.

Corresponding issue:
#3871

Testing

Added tests for the new behaviour

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