I can't find an RFC about this, but it looks like something similar has been proposed in the past, with a slightly different API.
> In URIs for MIME text/plain documents RFC 5147 specifies a fragment identifier for the character and line positions and ranges within the document using the keywords "char" and "line". Some popular browsers do not yet support RFC 5147.[5] The following example identifies lines 11 through 20 of a text document: http://example.com/document.txt#line=10,20