message: Add references to lexer modes and custom token patterns to the lexer tutorial
diff: @@ -121,9 +121,15 @@ Note that:
  - The **order** of Token definitions passed to the Lexer is **important**.
  The first PATTERN to match will be chosen not the longest.
  - - See how to resolve [Keywords vs Identifiers](https://github.com/SAP/chevrotain/blob/master/examples/lexer/keywords_vs_identifiers/keywords_vs_identifiers.js)
  + - See how to resolve [Keywords vs Identifiers](https://github.com/SAP/chevrotain/blob/master/examples/lexer/keywords_vs_identifiers/keywords_vs_identifiers.js).
  -- The Chevrotain Lexer is **stateless**, thus only a **single one per grammar** should ever be created.
  +- The lexer is **stateless**, thus only a **single one per grammar** should ever be created.
  +
  +- The lexer is **context unaware**, it lexes each token (pattern) individually.
  +
  + - If you need to distinguish between different contexts during the lexing phase, take a look at [Lexer Modes](../features/lexer_modes.md).
  +
  +- For more patterns requiring more complex constraints than a regular expression, take a look at [Custom Token Patterns](../features/custom_token_patterns.md).
  ## Using The Lexer
  