GTN language server to assist in training development

The [Galaxy language server (GLS)]( https://github.com/galaxyproject/galaxy-language-server) has started to support Galaxy Tool definitions in XML. It can by now lint Galaxy tools, bootstrap test & command sections, autocomplete user-inputs, and offers a variety of snippets.

It would be nice to explore if we can do the same for the GTN files.

* Snippets support
* checking/linting boxes
* ~check links (especially tool links and citations)~
* ~lint folder structure and metadata~
* ~check workflows (or run tests ...)~
* your ideas here ...

Given the GLS interacts with planemo we could also assist with bootstrapping a tutorial.