Zero-dependency library with no-std support for writing parsers in a concise functional style & with rich error-reporting.
Kinds of errors are distinguished via a user-defined Reason type, which signals what did
a parser expect.
A [ParsingError] can also have no reason, which will mean that the error is recoverable.
Some built-in parsers can have [core::convert::Infallible] as their error reason,
which means that any error the parser may ever return is recoverable.
The distinction between recoverable & fatal errors is important for parsers that need to try multiple options.
Error reporting with precise location in the source is facilitated by
constructing a [FullParsingError] with methods such as
[Parser::with_full_error], [ParsingError::with_src_loc]