Add love.window.getSafeArea (resolves issue #1437). Returns a rectangle (x, y, w, h) inside the window which is known to be unobstructed by a system title bar, the iPhone X notch, etc. Useful for making sure UI elements can be seen by the user.

Currently it only has a proper implementation on iOS and will return the window's full size otherwise.

src/modules/window/sdl/Window.h

@@ -66,6 +66,8 @@ public:
 	void setPosition(int x, int y, int displayindex) override;
 	void getPosition(int &x, int &y, int &displayindex) override;
 
+	Rect getSafeArea() const override;
+
 	bool isOpen() const override;
 
 	void setWindowTitle(const std::string &title) override;