Add openSUSE install instructions

Currently translated at 99.0% (621 of 627 strings)

Co-authored-by: Linerly <linerly@protonmail.com>
Translate-URL: https://weblate.nheko.im/projects/nheko/nheko-master/id/
Translation: Nheko/nheko

Currently translated at 100.0% (627 of 627 strings)

Co-authored-by: Priit Jõerüüt <nhkwlate@joeruut.com>
Translate-URL: https://weblate.nheko.im/projects/nheko/nheko-master/et/
Translation: Nheko/nheko

It seems like handling the message in a blocking manner is a no-go. I
have no idea how to fix that, so just use a queued connection for now...
(ASAN does not cooperate and just hides the crash D:)

fixes #842

Currently translated at 100.0% (627 of 627 strings)

Co-authored-by: Eldred HABERT <stuff@eldred.fr>
Translate-URL: https://weblate.nheko.im/projects/nheko/nheko-master/fr/
Translation: Nheko/nheko

Currently translated at 100.0% (627 of 627 strings)

Co-authored-by: DeepBlueV7.X <nicolas.werner@hotmail.de>
Translate-URL: https://weblate.nheko.im/projects/nheko/nheko-master/de/
Translation: Nheko/nheko

Currently translated at 100.0% (627 of 627 strings)

Co-authored-by: Jaron Viëtor <jaron@v8or.nl>
Translate-URL: https://weblate.nheko.im/projects/nheko/nheko-master/nl/
Translation: Nheko/nheko

Quality-of-life improvements

Added window role to image overlay

Might be unnecessary, but docs are unclear on that.

fixes #435

fixes #351

fixes #529

fixes #817
fixes sidebar not staying small after restart

fixes #824

fixes #519

fixes #840

Currently translated at 100.0% (612 of 612 strings)

Co-authored-by: Linerly <linerly@protonmail.com>
Translate-URL: https://weblate.nheko.im/projects/nheko/nheko-master/id/
Translation: Nheko/nheko