添加对while-do语句的支持 (#77)

Co-authored-by: jackfiled <xcrenchangjun@outlook.com>
Reviewed-on: PostGuard/Canon#77
Co-authored-by: ichirinko <1621543655@qq.com>
Co-committed-by: ichirinko <1621543655@qq.com>

Canon.Core/Enums/SemanticEnums.cs

@@ -65,7 +65,8 @@ public enum KeywordType
     And,
     Or,
     True,
-    False
+    False,
+    While
 }
 
 public enum OperatorType