Added AppendChar() example.

stringbuilder.mod/doc/tstringbuilder_appendchar.bmx

@@ -0,0 +1,14 @@
+SuperStrict
+
+Framework BRL.StringBuilder
+Import brl.standardio
+
+Local sb:TStringBuilder = New TStringBuilder
+
+Local chars:Int[] = [72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100, 33]
+
+For Local c:Int = EachIn chars
+	sb.AppendChar(c)
+Next
+
+Print sb.ToString()