added is T_3 rendering

Author: SKolodynski

isar2html2.0/src/isar2html/IsarSym2Latex.fs

@@ -227,6 +227,7 @@ namespace iml
                  ("\\{is T_0\\}","\\text{ is }T_0")
                  ("\\{is T_1\\}","\\text{ is }T_1")
                  ("\\{is T_2\\}","\\text{ is }T_2")
+                 ("\\{is T_3\\}","\\text{ is }T_3")
                  ("\\{up-directs\\}","\\text{ up-directs }")
                  ("\\{down-directs\\}","\\text{ down-directs }")
                  ("range(","\\text{range}(")