This change enables Splash to highlight multi-line comments that begin
with two asterisks, rather than just one. A test has also been added to
verify that documentation-style multi-line comments with an asterisk on
each line are also highlighted correctly.
This change makes it possible to implement custom token types, which is
really useful when building specialized grammars that use non-standard
token types.
This patch fixes syntax highlighting for the following scenario:
```
Type<GenericType>.call()
```
Highlighting generic types is especially tricky, since we want them to
be highlighted when appearing at the call site, like above - but we don’t
want to highlight them when they are being declared. Hopefully with this
fix all/most edge cases are covered.
