fix(plugintabs): enabling multiple file formats

[mfranzke]

@bmuenzenmeyer your overwrite with commit b82bd12 of the placeholders <<type>> and <<typeUC>> (to hardcoded scss) that are used within the script https://github.com/pattern-lab/patternlab-node/blob/dev/packages/plugin-tab/index.js now results in that only one file (and only scss filetype/language) could get configured within the patternlab-config.json.

It looks to me like that this happened by accident - I would than like to offer to fix this (and some other small parts) for this to work correctly again, if the change didn't happen on purpose.

[bmuenzenmeyer]

yes this looks like a bug to me - though only that portion. the intent of that commit was still to check for window.patternlab && window.patternlab.panels