overrides QTextEdit insert methods

fixes Chatterino#635
prepares for future implementation of Chatterino#79

Was a little bit hard to find the right combination for now. Pasting images from clipboard surpasses the check for dragging images in canInsertFromMimeData OMGScoots

src/widgets/helper/ResizingTextEdit.hpp

@@ -30,6 +30,9 @@ protected:
     void focusInEvent(QFocusEvent *event) override;
     void focusOutEvent(QFocusEvent *event) override;
 
+    bool canInsertFromMimeData(const QMimeData *source) const override;
+    void insertFromMimeData(const QMimeData *source) override;
+
 private:
     // hadSpace is set to true in case the "textUnderCursor" word was after a
     // space