Editor: Animate automatic completed text.

This gives a clear hint that something has changed.
And gets the attention of the author in the case he didn't
expect some kind of automatic brace or quote completion.

Change-Id: I33e383db9a1e797ecb285a407e46671f41be7051
Reviewed-by: Alessandro Portale <alessandro.portale@theqtcompany.com>

src/plugins/texteditor/texteditorconstants.h

@@ -40,6 +40,7 @@ enum TextStyle : quint8 {
     C_SEARCH_SCOPE,
     C_PARENTHESES,
     C_PARENTHESES_MISMATCH,
+    C_AUTOCOMPLETE,
     C_CURRENT_LINE,
     C_CURRENT_LINE_NUMBER,
     C_OCCURRENCES,