Export chat history to pdf (pr

Chat2pdf provides a way to export chat history to PDF/JPEG (the chat app could be whats/wechat/qq/etc). It uses screen record + image processing to save the chat history into PDF file or long picture/JPEG image.

Basic usage:

1. click record button and start to record chat history (when sliding screen, must keep the finger direction from bottom to up)

2. After record, click "Convert PDF" or "Convert JPEG" button to convert the screen record to PDF document or long picture/JPEG file.

3. View/share the generated PDF/JPEG.

Also support to convert any screen content to PDF, e.g. webpage