Add fixed-form support

[ZedThree]

Replaces #1

Updated to tree-sitter 0.23 and the latest (0.2.0) tree-sitter-fortran grammar.

Parses 100% of LAPACK.

It's a bit harder to check the wider corpus as lots of projects compile .f files in free-form mode, and so aren't valid fixed-form. There's also a surprising number of fixed-form files with tabs out there too, which obviously makes parsing them tricky when we're looking for any character in column 6 for a line continuation.

I've tried a couple of things for handling tabs, but not managed to get one to work. I think probably a sensible approach would be to basically not try to handle line continuations if we've seen a tab already on a given line.

@stadelmanma I've been having to do some manual futzing in order to update against the free-form grammar. Basically npm update doesn't seem to work locally for me, and I have to run node-gyp build in tree-sitter-fortran manually and copy some files across to node_modules in this project. This might be easier if we can publish the npm package for tree-sitter-fortran?

[ZedThree]

Hmm, I've copied the github workflows across, but they don't seem to have been picked up

[ZedThree]

@stadelmanma I sorted out my issues with npm update/install, and this now all seems to work fine.

This is now updated to the latest tree-sitter-fortran (0.5.1). It's slightly annoying to keep the external scanners in sync, I'm not sure there's a better way of doing that. While some bits can be reused, obviously line continuations have to be handled differently, and there's two or three places they creep in.