Allow set based indexing for including lines from files

Problem

Given

Lines 304 to 305 of file foo can be included in code-block using the following syntax

{{#include foo:304:305}}

Issue

The above format is less terse when including multiple lines from the same file e.g.,

{{#include foo:304:305}}
{{#include foo:307}}
{{#include foo:309:318}}

Proposed Solution

Use , to specify multiple ranges at once e.g.,

{{#include foo:304:305,307,309:318}}

Use +/- to perform operations on ranges e.g.,

{{#include foo:304:318-[306,308]}}

In BNF form, this translates to:

arg := index | '::' index | index ':' | index ':' index 
factor := '-' | '+'
bracketedList := '[' argList ']' 
argList := arg | arg ',' argList | rangeExpression
rangeExpression := bracketedList factor bracketedList | arg factor bracketedList | arg factor arg

Notes

No response

Begin by locating the existing parser and tests for #include line ranges; the issue names no file or test path. Use the examples and BNF as the behavior to verify, including comma-separated ranges and +/- expressions. Done means the proposed syntax works for the shown cases and existing range behavior remains intact.