【New Feature】Support PDF reading

[feloxx]

Support PDF reading

At the moment there are Markdown editors and text editors.

Need to achieve a PDF editor, first realize the function of reading.

Explore

Qt 5.15.2 already comes with the PDF module, but you need to compile the source code to get it.

High implementation costs.

We can do this by importing external packages, which is cheaper than compiling source code.

I found the following external packages:

• https://github.com/Archie3d/qpdf
• https://github.com/paulovap/qtpdfium
• https://github.com/qt-labs/qtpdf
• https://github.com/gnab/remark
• https://github.com/hiroppy/fusuma

Implement the list

• [ ] Open logic choose
• [ ] PDF view window
• [ ] Successful introduction
• [ ] Successful Reading