Improve Formie.js loading to only load when form is visible

[engram-design]

To get around cases where Formie's JS doesn't need to run immediately (the form is hidden in a modal), we should use something like IntersectionObserver to detect when the form is visible on the page to then run the JS. This will also help with page performance when including things like captchas.

https://github.com/verbb/formie/issues/1392 https://github.com/verbb/formie/issues/1386

[hassanmah]

@engram-design any updates on this? All my forms are in modals

[engram-design]

This is available for Formie 3 (starting in 3.0.0-beta.1), we're not looking to make this available in Formie 2.x.

[engram-design]

Added in 3.0.0