Make titiler-xarray a dependency for titiler-cmr?

[maxrjones]

I'm wondering if it would be possible to depend on titiler-xarray for titiler-cmr rather than having a separate XarrayReader in this library? The benefit of this would be reducing code duplication. For example, the code being discussed in #34 exists separately in both libraries. The reader module in titiler-cmr has very few differences from the reader module in titiler-xarray, with the exception of having an additional MultiFilesBandsReader and a different approach to caching datasets.

[vincentsarago]

@maxrjones We will do this once we've done developmentseed/titiler-multidim#68

for now titiler-xarray is not publish on pypi