Features suggestion

Hi,

Great plugin. I’ve been using it on a project and wanted to ask whether you’d consider two small enhancements:

1. Support CSS variables for offset height
   It would be useful to allow offset height to accept CSS variables (e.g. var(–offset-height)) instead of only numeric values.

Use case: when the value differs between desktop and mobile. For example, in my setup I already compute it in JS and update a :root CSS variable on resize, so being able to reference that variable directly in the plugin configuration would simplify things.

2. Global defaults for duration / delay / threshold
   It would be helpful to define global default values (via filter or constants, not necessarily UI) for duration, delay, and threshold.

Use case: If the current plugin defaults are not the ones normally used in a project, it gets tedious to have to change them when adding every animation.
I’d also be happy to contribute these changes via PRs, but I noticed the github repository appears to be updated only up to version 1.1.4, so not sure how to proceed with that.

Thanks for considering these suggestions.