Add .gitreview file

`git-review` is a command line tool for interacting with Gerrit.
Some IDEs offer support for this tool, either natively or through
plugins. The tool relies on a configuration file, .gitreview. Adding
this configuration file to our repositories simplifies initial setup
for contributors that use the tool directly or through their IDE of
choice.

The configuration file adds a remote called 'gerrit'. This is the
default for the tool, and also the name set for
codereview.qt-project.org by Qt's `init-repository` script. Thus,
the configuration should work seamlessly alongside other repository
helpers.

Task-number: QTBUG-132604
Pick-to: 6.9 6.8
Change-Id: Ib5660759ab2cda9387ce6ca48278cef1e8488cfe
Reviewed-by: Samuel Gaist <[email protected]>

Author: paulwicking

.gitreview

@@ -0,0 +1,4 @@
+[gerrit]
+host=codereview.qt-project.org
+project=qt/qtqa
+defaultbranch=dev