Update MessageTokenizer.cs (#294)

Author: LaurieCheers-unity

com.unity.robotics.ros-tcp-connector/Editor/MessageGeneration/MessageTokenizer.cs

@@ -258,7 +258,7 @@ private MessageToken NextCommentToken()
  private MessageToken NextSeperator()
  {
  string token = ReadUntilNewLineAndTrim();
- if (token.Equals("---"))
+ if (token.StartsWith("---"))
  {
  reader.Read();
  lineNum++;