v21.09.1

Changelog:

Åke Engelbrektson (1):

• Update timeshift-sv.po

Alan01 (1):

• Update timeshift-da.po

Butterfly (1):

• Update tr.po

DuckSoft (1):

• fix: add which to dependencies

Hugo Carvalho (1):

• Update Portuguese translation

Hsiu-Ming Chang (1):

• Update zh_TW translation

Kota Kato (1):

• Update po/timeshift-ja.po

Peter Dyson (1):

• Warn against swapfiles within target snapshot subvolumes

Philipp Kiemle (1):

• Update de translation

Pjotr123 (1):

• Update timeshift-nl.po

Tony George (7):

• Fix #676 Build fails with xapp 2.0.0
• Fix #676 Update references to GLib.Object
• Fix #425, #753, #755
• Fix #589
• Fix #186
• Fix compiler warnings
• Update README