Add PDF support

[Jesper-Hustad]

There has been feedback that people are trying to use PDF files with the tool.

Since PDF files are quite common in the graphic design world it would probably also be convenient to add support for this as well.

This would be implemented by getting the first page of a PDF file, converting it into image data that can be handled by the JavaScript, run normally from there on out.

Requirements are:

• small code size to keep the tool quick for slow internet users
• relatively quick processing time, should preferably not take more than 1 second.
• no user interface options, just take the first pdf page

[diegoherrer4]

Is this issue still available? Would love to help