AptaTrans jupyter notebook (#146)

Adds a jupyter notebook for AptaTrans where it is possible to: (i) train
the model via `lightning`; (ii) load pretrained weights; and (iii) use
the model in combination with MCTS to rank aptamer candidates.

This PR resolves #145 and is stacked on #92.

Author: NennoMP

.github/workflows/test.yml

@@ -121,7 +121,7 @@ jobs:
 
       - name: Run jupyter notebooks
         run: |
-          python -m pip install jupyter nbconvert ipykernel
+          python -m pip install jupyter nbconvert "ipykernel>=6.29.5,<7.0.0"
           python -m ipykernel install --user --name=python3 --display-name "Python 3 (CI)"
           bash build_tools/run_all_notebooks.sh