Use metpy.parse_cf() to detect x/y

[ahuang11]

Here, it seems like lat/lon is hardcoded:
https://github.com/developmentseed/titiler-xarray/blob/main/titiler/xarray/reader.py#L52

One way to address finding x/y is using https://unidata.github.io/MetPy/latest/api/generated/metpy.xarray.html

[abarciauskas-bgse]

@ahuang11 thank you for this issue and sorry I never responded. I tried using metpy and it worked quite nicely but I found it was a too heavy a dependency for our lambda at this time. I'll leave this open for now since we may migrate off lambda in the future and could leverage metpy then.