PR Template (#1446)

* created a PR template

* Changed to better fit other standard jupyter repo PR templates

* changed contributing page and added space

---------

Co-authored-by: Jonah Jung <[email protected]>

Author: jonahjung22

.github/workflows/pull_request_template.md

@@ -0,0 +1,25 @@
+<!--
+Thank you for contributing to Jupyter AI! Please fill out the following items to submit a pull request.
+See the contributing guidelines for more information:
+https://jupyter-ai.readthedocs.io/en/latest/contributors/
+-->
+
+## References
+
+<!-- Note issue numbers this pull request addresses (should be at least one, see contributing guidelines above). -->
+
+<!-- Note any other pull requests that address this issue and how this pull request is different. -->
+
+## Code changes
+
+<!-- Describe the code changes and how they address the issue. -->
+
+## User-facing changes
+
+<!-- Describe any visual or user interaction changes and how they address the issue. -->
+
+<!-- For visual changes, include before and after screenshots or GIF/mp4/other video demo here. -->
+
+## Backwards-incompatible changes
+
+<!-- Describe any backwards-incompatible changes to Jupyter AI public APIs. -->