[Enhancement] Add Parser Support for Invalid Syntax Literals

[bgribaudo]

Describe the solution you'd like
Power Query expressions can contain "invalid syntax literals" (unsure the official name), a syntax construct in the form of #!" … " which is not mentioned in the official language specification.

To enable this parser to fully parse the section documents created by Microsoft Excel and Power BI, both of which can output invalid syntax literals, would it make sense to extend the parser to support these literals?

Example (pulled verbatim from a Power BI file):

section Section1;

shared Query1 = let
    Source = #!"let a"
in
    Source;

Additional context
For more details on these literals, see https://github.com/MicrosoftDocs/powerquery-docs/issues/12.

[JordanBoltonMN]

It's not the highest priority but I don't think it'll be difficult to implement.. I'll look into it once I'm back in office.

[JordanBoltonMN]

It should be relatively easy to implement, but is marked as low priority as users won't run into a the verbatim literal in a regular work flow.

[bgribaudo]

Sounds good. Thank you, @JordanBoltonMN!