Allow filetype-specific usage instructions

[ml-evs]

e.g., yadg should be allowed to say, "here is my usage template for these formats, and here it is for these other formats":

e.g.,

usage: 
    - method: python
      setup: yadg
      command: yadg.extractors.biologic_extract({{ input_type }}, {{ input_path }})
      filetypes: ["biologic-mpr", "biologic-mpt"]
    - method: python
      setup: yadg
      command: yadg.extractors.xrd_extract({{ input_type }}, {{ input_path }})
      filetypes: ["panalytical-xrdml"]

This feels a bit kludgey (and would need validation outside of LinkML to make sure that the types match the support_filetypes, and that all cases are covered), but is probably preferable to having to add multiple extractors in the registry?

[PeterKraus]

Perhaps reusing supported_filetypes entry for each usage might be the way to do it. However, validation is an issue. I've asked on the linkml discussion board, let's see if there's an easy way.

[PeterKraus]

In lieu of the galvani entry above, should we just add the field without any linkml-side validation for now?