Format regions as-is

[srhickma]

Allow specific regions in the parse tree to be formatted as-is, by copying the exact text from the input string. This is more complicated than simply formatting without patterns, as this requires the entire input section to be tokenized (no ignored tokens). To achieve this, we will need to be able to look up the position of two "bounding" tokens in the input string, so that we can copy the text between them to the output.

[srhickma]

This can be achieved by simply scanning the entire "as-is" region into a single token, including all whitespace, etc.