PSyKAl-lite code tracker

Nobody has claimed this yet.

### Are there any linked Issues or Pull Requests?

mo-alistairp/lfric_apps#1

### Brief description

This issue helps store and document the PSyKAl-lite code tracker I made, as I won't have time to fully implement it any more. I'm leaving this here in case anyone has the time/want to pick this up in the future.

### Further details of the issue.

I'm storing the code for this in a PR in my fork of apps (mo-alistairp/lfric_apps#1). I've done it that way to avoid a stale PR clogging up the main repo.

It's final home was not meant to be in the top of the repository directory but implemented into either a Cylc suite or GitHub action. It does at least function in its current state. It will scan all the Fortran code in the directory you point it towards and then either either a `.txt` and/or a `.json` file on request containing an alphabetised list of PSyKAl-lite code. In an implemented situation this could then be compared with a version of this file on trunk to see whether PSyKAl-lite code has been either added/removed and notify the correct person (similar to KGO checks).

It can simply be run using Python and it'll generate the requested files. Note that it does use type-hinting so needs to be Python 3.10 or newer.

I have put this in the LFRic Apps repository but could easily be moved to check LFRic core too with a simple path change. Ideally this script would be used to check both simultaneously.

Start by reviewing the existing implementation in mo-alistairp/lfric_apps#1 and confirm its Python 3.10 requirements. Determine how it should be integrated into a Cylc suite or GitHub Action for both LFRic Apps and LFRic core. Done should include generating the requested .txt and/or .json tracker output and a way to compare it with trunk and notify the appropriate person.

Written by the indexing model from the issue text.