JAX + DDPG docs fix (#229)

Author: vwxyzjn

.github/pull_request_template.md

@@ -17,7 +17,7 @@
 - [ ] I have updated the tests accordingly (if applicable).
 
 If you are adding new algorithms or your change could result in performance difference, you may need to (re-)run tracked experiments. See https://github.com/vwxyzjn/cleanrl/pull/137 as an example PR. 
-- [ ] I have contacted @vwxyzjn to obtain access to the [openrlbenchmark W&B team](https://wandb.ai/openrlbenchmark) (**required**).
+- [ ] I have contacted [vwxyzjn](https://github.com/vwxyzjn) to obtain access to the [openrlbenchmark W&B team](https://wandb.ai/openrlbenchmark) (**required**).
 - [ ] I have tracked applicable experiments in [openrlbenchmark/cleanrl](https://wandb.ai/openrlbenchmark/cleanrl) with `--capture-video` flag toggled on (**required**).
 - [ ] I have added additional documentation and previewed the changes via `mkdocs serve`.
     - [ ] I have explained note-worthy implementation details.

docs/rl-algorithms/ddpg.md

@@ -14,6 +14,7 @@ Reference resources:
 
 * :material-github: [sfujim/TD3](https://github.com/sfujim/TD3)
 * [Deep Deterministic Policy Gradient | Spinning Up in Deep RL](https://spinningup.openai.com/en/latest/algorithms/ddpg.html)
+* :material-github: [ikostrikov/jaxrl](https://github.com/ikostrikov/jaxrl) (helpful reference when implemented [`ddpg_continuous_action_jax.py`](https://github.com/vwxyzjn/cleanrl/blob/master/cleanrl/ddpg_continuous_action_jax.py))
 
 ## Implemented Variants