fix readme codeblock highlghts

Author: norlandrhagen

README.md

@@ -24,7 +24,7 @@ ds = ds.proj.assign_crs(spatial_ref_crs={"EPSG":4326})
 print(ds)
 ```
 
-```
+```python
 pyramid = create_pyramid(
     ds, 
     levels=2, 
@@ -36,7 +36,7 @@ print(pyramid.encoding)
 print(pyramid.dt)
 ```
 
-```
+```python
 # Optional: Write to Zarr
 !pip install obstore zarr
 from obstore.store import from_url