Upgrade sdk qpdf 0.9.2 (#27)

* update flatpak SDK, QPDF and fix toast dismiss logic

* update metainfo

bugfix: Handle null value from callback result if file chooser is can…

…celed.

update metainfo

refactor: replace deprecated widgets

refactor: use single yaml for flatpak build.
refactor: improve css
refactor: improve debug logging

Fix translation and windows icon

- fix translation, init gettext.
- fix icon on windows.
- set version from meson project.

Dismiss failed toasts on success.

- store all toasts in an array, dismiss every other toast on successful decryption.
- bump version to 0.07

Transition to libadwaita About Window.

- bump flatpak platform to 43.
- bump version to 0.06

update README

bump version to 0.04

bump version to 0.03