Add template to text watermark

[Clouz]

Using "text/template" advance text watermark can be improved adding pages numbering function

[ajaxray]

Hi @Clouz,

I was thinking, people generally use fixed-text watermarking. I didn't see this use case before. However, I'll check if we can improve the tool with template/placeholder based text.

Thanks a lot for the suggestion! 👍🏼

[ajaxray]

Just have seen your PR #14 Will check it very soon. Thanks ❤️

[ajaxray]

The feature is included in this release.