Allow crs as class name to match projection

[ahuang11]

Closes #1303

import xarray as xr
import hvplot.xarray

ds = xr.tutorial.open_dataset("air_temperature").isel(time=0)
ds.hvplot("lon", "lat", projection="PlateCarree", crs="PlateCarree")

[maximlt]

It looks like this needs to be updated:

https://github.com/holoviz/hvplot/pull/1332/files#diff-784450df58c4440b52a1431a7402766102b3d56ad7f1fbc30a4ff2c2fef24352R317-R320

Together with the project/crs docstring in the converter and the doc in the geographic user guide and customization guide.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.36%. Comparing base (e5e71d6) to head (c15317f).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1332   +/-   ##
=======================================
  Coverage   87.36%   87.36%           
=======================================
  Files          50       50           
  Lines        7471     7472    +1     
=======================================
+ Hits         6527     6528    +1     
  Misses        944      944           

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[maximlt]

Thanks!!!