Add the processing code from fatiando/data

Author: leouieda

environment.yml

@@ -1,4 +1,4 @@
-name: fatiando-data-CHANGEME
+name: fatiando-data-britain-magnetic
 channels:
   - conda-forge
   - defaults
@@ -8,14 +8,10 @@ dependencies:
   - numpy
   - jupyterlab
   - matplotlib
-  - xarray
-  - netcdf4
   - pyproj
   # PyGMT for plotting
   - pygmt==0.4.1
   - gmt==6.2.0
   # Fatiando
   - pooch>=1.0
-  - harmonica==0.4.*
   - verde==1.6.1
-  - boule==0.3.*