Fix __init__.py file to import from local "examples" dir.

Without this fix, importing torch_harmonics had run into a module import error
when trying to execute:
```import examples```

torch_harmonics/__init__.py

@@ -34,4 +34,4 @@ __version__ = '0.6.1'
 from .sht import RealSHT, InverseRealSHT, RealVectorSHT, InverseRealVectorSHT
 from . import quadrature
 from . import random_fields
-import examples
+from . import examples