Log Message:
pluma: update to 1.22.1

### pluma 1.22.1

  * tx: sync with transifex
  * update installation instructions and fix spelling and old reference
  * Help: replace link linkend with xref linkend
  * help: update copyright
  * Use ITS in docbook article info, validate with dbits schemas
  * Upgrade the manual to docbook 5.0