add PDFsam Basic

[philclifford]

Closes #710

Note the free app is called pdfsam-basic

A separate licensable (free trial) Electron-based product (PDFsam Visual) is also available but will need its own PR (ready and tested if wanted)

Also their chosen style is indeed PDFsam and not PDFSam

deb-get show pdfsam-basic pdfsam-visual |grep -v -e '\['
PDFsam Basic
  Package:	pdfsam-basic
  Repository:	90-contribs
  Updater:	deb-get
  Installed:	5.0.3-1
  Published:	5.0.3
  Architecture:	amd64
  Download:	https://github.com/torakiki/pdfsam/releases/download/v5.0.3/pdfsam_5.0.3-1_amd64.deb
  Website:	https://pdfsam.org/
  Summary:	PDFsam (PDF Split And Merge) Basic is a free and open source, multi-platform software designed to extract pages, split, merge, mix and rotate PDF files.
PDFsam Visual
  Package:	pdfsam-visual
  Repository:	90-contribs
  Updater:	deb-get
  Installed:	4.3.0
  Published:	4.3.0
  Architecture:	amd64
  Download:	https://github.com/torakiki/pdfsam-visual-public/releases/download/v4.3.0/pdfsam-visual_4.3.0_amd64.deb
  Website:	https://pdfsam.org/
  Summary:	PDFsam Visual is a powerful tool to visually combine PDF files, rearrange pages, compress, extract or delete pages, split, merge, rotate, encrypt, decrypt, repair, resize pages, extract text, convert to grayscale, crop PDF files.