Add proguard rules for SDL2

Based on existing work by @AntTheAlchemist on SDL3 branch.

android-project/app/proguard-rules.pro

@@ -15,3 +15,84 @@
 #-keepclassmembers class fqcn.of.javascript.interface.for.webview {
 #   public *;
 #}
+
+-keep,includedescriptorclasses,allowoptimization class org.libsdl.app.SDLInputConnection {
+    void nativeCommitText(java.lang.String, int);
+    void nativeGenerateScancodeForUnichar(char);
+}
+
+-keep,includedescriptorclasses class org.libsdl.app.SDLActivity {
+    # for some reason these aren't compatible with allowoptimization modifier
+    boolean supportsRelativeMouse();
+    void setWindowStyle(boolean);
+}
+
+-keep,includedescriptorclasses,allowoptimization class org.libsdl.app.SDLActivity {
+    java.lang.String nativeGetHint(java.lang.String); # Java-side doesn't use this, so it gets minified, but C-side still tries to register it
+    boolean onNativeSoftReturnKey();
+    void onNativeKeyboardFocusLost();
+    boolean isScreenKeyboardShown();
+    android.util.DisplayMetrics getDisplayDPI();
+    java.lang.String clipboardGetText();
+    boolean clipboardHasText();
+    void clipboardSetText(java.lang.String);
+    int createCustomCursor(int[], int, int, int, int);
+    void destroyCustomCursor(int);
+    android.content.Context getContext();
+    boolean getManifestEnvironmentVariables();
+    android.view.Surface getNativeSurface();
+    void initTouch();
+    boolean isAndroidTV();
+    boolean isChromebook();
+    boolean isDeXMode();
+    boolean isTablet();
+    void manualBackButton();
+    int messageboxShowMessageBox(int, java.lang.String, java.lang.String, int[], int[], java.lang.String[], int[]);
+    void minimizeWindow();
+    int openURL(java.lang.String);
+    void requestPermission(java.lang.String, int);
+    int showToast(java.lang.String, int, int, int, int);
+    boolean sendMessage(int, int);
+    boolean setActivityTitle(java.lang.String);
+    boolean setCustomCursor(int);
+    void setOrientation(int, int, boolean, java.lang.String);
+    boolean setRelativeMouseEnabled(boolean);
+    boolean setSystemCursor(int);
+    boolean shouldMinimizeOnFocusLoss();
+    boolean showTextInput(int, int, int, int);
+}
+
+-keep,includedescriptorclasses,allowoptimization class org.libsdl.app.HIDDeviceManager {
+    boolean initialize(boolean, boolean);
+    boolean openDevice(int);
+    int sendOutputReport(int, byte[]);
+    int sendFeatureReport(int, byte[]);
+    boolean getFeatureReport(int, byte[]);
+    void closeDevice(int);
+}
+
+-keep,includedescriptorclasses,allowoptimization class org.libsdl.app.SDLAudioManager {
+    int[] getAudioOutputDevices();
+    int[] getAudioInputDevices();
+    int[] audioOpen(int, int, int, int, int);
+    void audioWriteFloatBuffer(float[]);
+    void audioWriteShortBuffer(short[]);
+    void audioWriteByteBuffer(byte[]);
+    void audioClose();
+    int[] captureOpen(int, int, int, int, int);
+    int captureReadFloatBuffer(float[], boolean);
+    int captureReadShortBuffer(short[], boolean);
+    int captureReadByteBuffer(byte[], boolean);
+    void captureClose();
+    void audioSetThreadPriority(boolean, int);
+    native int nativeSetupJNI();
+    native void removeAudioDevice(boolean, int);
+    native void addAudioDevice(boolean, int);
+}
+
+-keep,includedescriptorclasses,allowoptimization class org.libsdl.app.SDLControllerManager {
+    void pollInputDevices();
+    void pollHapticDevices();
+    void hapticRun(int, float, int);
+    void hapticStop(int);
+}