Add hook to turn off auto-submission of 2FA form

[eric-michel]

Is your enhancement related to a problem? Please describe.

This is related to #722.

In the process of creating our trusted device addon to this plugin, we're having to use a bit of a hack to remove the auto-submission feature from the 2FA form (so that the user has an opportunity to check the "trust this device" checkbox before clicking Verify).

// Auto-submit if it's the expected length.
if ( expectedLength && value.replace( / /g, '' ).length == expectedLength ) {
	if ( undefined !== form.requestSubmit ) {
		form.requestSubmit();
		form.submit.disabled = "disabled";
	}
}

Proposed Solution

Add a hook that allows for a theme or plugin to turn off the auto-submit feature.

Designs

No response

Describe alternatives you've considered

No response

Please confirm that you have searched existing issues in this repository.

Yes

[kasparsd]

This would be a useful feature. Would you have the capacity to create a pull request that implements this?

[eric-michel]

I can definitely give it a shot! Let me see if I can carve out a bit of time over the next week or so.