Fix automatic reload of files saved with QSaveFile

Summary:
Files saved with QSaveFile don't get dirty. They are deleted and replaced.
Thus, inotify and KDirWatch don't emit a "dirty" signal (which is the correct behaviour).
Listening for the "created" signal of KDirWatch allows us to get notified on replaced files.

BUG: 384185

Test Plan:
Opened a markdown document in Okular.
Edited and saved the document with Kate.
The file is reloaded in Okular as expected.

Reviewers: aacid

Reviewed By: aacid

Subscribers: sander, rkflx, #okular

Tags: #okular

Differential Revision: https://phabricator.kde.org/D7671