search & replace, set fovcus on doc after findNext

prevent to go back to the editor when doing the following
    - CTRL+F (find using selection, focus is now on the search widget)
    - F3 (find match)
    => click was necessary to give focus again on the editor, e.g to DEL

src/u_search.pas

@@ -539,6 +539,7 @@ begin
     fHasSearched := true;
     fHasRestarted := false;
     chkFromCur.Checked := true;
+    fDoc.setFocus;
   end;
   updateImperative;
 end;