Add TextField Background Opacity Support

[Patzi275]

Describe your idea

Enable pdf-lib to adjust background opacity of TextField objects. This enhancement would allow users to customize PDF forms and documents more flexibly. Here's a proposed API snippet:

const field = form.createTextField('favorite.superhero')
field.setText('One Punch Man')
field.addToPage(page, { 
    // ...
    backgroundOpacity: 0.0
})

What problem are you trying to solve?

Current pdf-lib lacks programmable control over TextField background opacities, limiting customization options for PDF forms and documents.

Why does this matter to you?

Enhances visual appeal and usability of PDF documents, catering to a wide range of pdf-lib users dealing with form generation and document customization.

Would others find this helpful?

Yes, I cannot give you an number honestly

Are you interested in implementing your proposal?

No

Why are you submitting a proposal?

My primary goal is to contribute to the improvement of pdf-lib by highlighting a feature gap.

Additional Notes

No response