Create rdf/shacl-utils module

[jsheunis]

I'm encountering, several times already, the need to manipulate rdf data or shacl shapes in a general way, e.g. to interpret RDF lists and convert them to js arrays. Most of this functionality is currently contained in composables where they are required, e.g. in the shapes composable: https://github.com/psychoinformatics-de/shacl-vue/blob/main/src/composables/shapedata.js

This needs to be factored out into a separate module. Also, need to check if there aren't existing functionality in the tools that are used, e.g. rdf-ext, that could be used instead of creating something custom.