id setting should apply to the form element too

[coreyworrell]

Description

The default autocomplete form has no id attribute, so you are unable to use external buttons to submit the form (<button form="form-id">Submit</button>).

Reproduction

Preview →

Steps

1. Enter search term
2. Press enter on keyboard, see alert popup that form was submitted.
3. Press escape key on wide screen or click "Cancel" button on narrow screen to hide autocomplete panel
4. Click "External submit" button to submit the form.
5. No alert pops up this time.
6. Manually add the id="form-id" attribute to the generated autocomplete form and click the "External submit" button and see the popup does show.

Expected behavior

The <form> element would receive the passed id. This is also useful when we are replacing an existing form with the autocomplete (JavaScript fallback), which already has an id. So if we can assign the id here, the same button can be used to submit whether it's the fallback form or the autocomplete form.

Environment

• OS: Linux
• Browser: Firefox
• Autocomplete version: 1.9.2