Is your feature request related to a problem? Please describe.
The FhirPath Expression and derived classes have support for location information however this is never populated by the sprache parser.

Describe the solution you'd like
During the parsing of a fhirpath expression optionally support the inclusion of the position information for each sub-expression in the AST.

Additional context
I plan to use this information in the fhirpath-lab project through my open source FhirPath Expression validator nuget package.
This will help significantly with error messages and also highlighting expressions in related tooling.