Allow selction of default pdf reader in settings/hamburger menu

[e-alfred]

Hello,

now that you support pdf files (which is quite awesome), it would be great to be able to select which viewer should be used (either Nextcloud built in or the Ebook reader app).

[Yetangitu]

See nextcloud/viewer#2393 and owncloud/core#30306 for a proposed solution to this problem, it should really be handled in Core instead of in individual apps as the latter would lead to app turf wars fighting to the last bit of which app gets to handle which mime type.

[Yetangitu]

In v1.2.0 I implemented a temporary personal preferences section for this purpose where you can define for which file types Reader should be the default viewer:

Once nextcloud/viewer#2393 and owncloud/core#30306 have been implemented this section will be removed.

v1.2.0 will be released Real Soon Now...