Add missing links (#111)

docs/hierarchy.md

@@ -88,6 +88,9 @@
   - [deal-with-incomplete-models](future-work/learning-module-improvements/deal-with-incomplete-models.md)
   - [implement-test-gnns-to-model-object-behaviors-states](future-work/learning-module-improvements/implement-test-gnns-to-model-object-behaviors-states.md)
   - [deal-with-moving-objects](future-work/learning-module-improvements/deal-with-moving-objects.md)
+  - [support-scale-invariance](future-work/learning-module-improvements/support-scale-invariance.md)
+  - [improve-handling-of-symmetry](future-work/learning-module-improvements/improve-handling-of-symmetry.md)
+  - [use-better-hypothesis-priors](future-work/learning-module-improvements/use-better-hypothesis-priors.md)
 - [motor-system-improvements](future-work/motor-system-improvements.md)
   - [implement-policy-switching-learning-vs-inference](future-work/motor-system-improvements/implement-policy-switching-learning-vs-inference.md)
   - [bottom-up-exploration-policy-for-surface-agent](future-work/motor-system-improvements/bottom-up-exploration-policy-for-surface-agent.md)
@@ -96,6 +99,8 @@
   - [learn-policy-using-rl](future-work/motor-system-improvements/learn-policy-using-rl.md)
   - [decompose-goals-into-subgoals-communicate](future-work/motor-system-improvements/decompose-goals-into-subgoals-communicate.md)
   - [interpret-goal-states-in-motor-system-switch-policies](future-work/motor-system-improvements/interpret-goal-states-in-motor-system-switch-policies.md)
+  - [reuse-hypothesis-testing-points](future-work/motor-system-improvements/reuse-hypothesis-testing-points.md)
+  - [simple-cross-modal-policy](future-work/motor-system-improvements/simple-cross-modal-policy.md)
 - [voting-improvements](future-work/voting-improvements.md)
   - [use-pose-for-voting](future-work/voting-improvements/use-pose-for-voting.md)
   - [outline-routing-protocol-attention](future-work/voting-improvements/outline-routing-protocol-attention.md)