Update instructions for Android in README.md file (pull #2263)

Upgrade GitHub Actions workflow to macOS 12

.github/workflows/javacv.yml

@@ -17,7 +17,7 @@ jobs:
         with:
           sudo: false
   macosx-x86_64:
-    runs-on: macos-11
+    runs-on: macos-12
     steps:
       - uses: bytedeco/javacpp-presets/.github/actions/deploy-macosx@actions
       - uses: mxschmitt/[email protected]

README.md

@@ -97,6 +97,7 @@ IntelliJ IDEA (Android 7.0 or newer):
  2. Copy all the JAR files into the `app/libs` subdirectory.
  3. Navigate to File > Project Structure > app > Dependencies, click `+`, and select "2 File dependency".
  4. Select all the JAR files from the `libs` subdirectory.
+ 5. In the AndroidManifest.xml add `android:extractNativeLibs="true"`
 
 After that, the wrapper classes for OpenCV and FFmpeg, for example, can automatically access all of their C/C++ APIs: