[Feature request] add filler function

[nikazz]

Please Add the ability to fill out forms in pdf!

[Archie3d]

This is rather a pdf.js feature request. Seems that they've added forms support recently (https://github.com/mozilla/pdf.js/issues/7613), I need to check how it works regarding the outstanding issues (https://github.com/mozilla/pdf.js/labels/4-form-acroform), and how to back port the new version in here.

[nikazz]

thanks, found)))