move torch to extras_require for optional install

Author: CosmoMatt

.github/workflows/docs.yml

@@ -29,7 +29,7 @@ jobs:
         pip install jaxlib
         pip install -r requirements/requirements-core.txt
         pip install -r requirements/requirements-docs.txt
-        pip install .
+        pip install .\[torch\]
   
     - name: Build Documentation
       run: |

requirements/requirements-core.txt

@@ -3,5 +3,4 @@ numpy>=1.20
 colorlog
 pyyaml
 jax>=0.3.13
-jaxlib
-torch
+jaxlib

setup.py

@@ -33,4 +33,5 @@
     packages=find_packages(),
     include_package_data=True,
     pacakge_data={"s2fft": ["default-logging-config.yaml"]},
+    extras_require={"torch": ["torch"]},
 )