Give focus to VST3 UI when instructed by the host

Signed-off-by: falkTX <falktx@falktx.com>

distrho/src/DistrhoUIVST3.cpp

@@ -242,6 +242,8 @@ public:
 
     v3_result onFocus(const bool state)
     {
+        if (state)
+            fUI.focus();
         fUI.notifyFocusChanged(state);
         return V3_OK;
     }