Remove QtAndroidExtras module and add note about its state in Qt 6HEADdev

The JNI utilities (i.e. QJniObject, QJniEnvironment) are already under
qtbase as public APIs.

Permission handling is now under QCoreApplication::{check,request}Permission
and QPermission namespace.

Some of the QtAndroid namespace functions are now under QNativeInterface's
QAndroidApplication, this includes:
* sdkVersion()
* hideSplashScreen()
* context() and isActivityContext()
* runOnAndroidMainThread()

The remaining APIs are now moved as private APIs under qtbase
ee05af296f65e240f64db6470cdddafbddbf2fa3. That is until we add
new cross-platform APIs to replace their functionalities like
Intents handling, starting activites and working with Services.

Task-number: QTBUG-83251
Task-number: QTBUG-84382
Pick-to: 6.2
Change-Id: Id077f8cbbe223a987916f737fad6088fb58e470d
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>

1 files changed, 30 insertions, 0 deletions

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..ebe23d5
--- /dev/null
+++ b/README.md
@@ -0,0 +1,30 @@
+# QtAndroidExtras
+
+**The QtAndroidExtras module has been deprecated and is no longer part of Qt.**
+
+The functionality of the module has been incorporated into other parts of Qt, or in some cases removed due to being obsolete or better suited as cross platform APIs.
+
+For more details, see [QTBUG-84382](https://bugreports.qt.io/browse/QTBUG-84382) in the Qt issue tracker.
+
+## Porting away from QtAndroidExtras
+
+To learn more about how to port from QtAndroidExtras to alternative APIs please visit the [Qt 6 porting guide](https://doc.qt.io/qt-6/portingguide.html).
+
+## Working on Qt 5
+
+To work on patches for the Qt 5 series, check out a local branch of the relevant Qt version, e.g.:
+
+```bash
+$ git checkout 5.15
+Branch '5.15' set up to track remote branch '5.15' from 'origin' by rebasing.
+Switched to a new branch '5.15'
+```
+
+## Going back in time
+
+To inspect the code in the `dev` branch prior to its removal, follow these steps:
+
+```bash
+$ git checkout -b my-dev dev~1
+Switched to a new branch 'my-dev'
+```