tacoreader dependency causes issues for the conda-forge receipe

[giswqs]

tacoreade is not yet available on conda-forge, but terratorch pins tacoreader==0.5.6, which is causing issues for the terratorch conda-forge recipe. Unless it is absolutely required, consider making it an optional dependency. Otherwise, the terratorch conda-forge recipe will not be updated until tacoreader is also available on conda-forge.

conda-forge/terratorch-feedstock#19

[romeokienzler]

@giswqs @rosielickorish will look into it, thanks so much!