Move license to footer (#400)

* Move license to footer

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: Andrew Huang <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

_config.yml

@@ -76,16 +76,16 @@ bibtex_bibfiles:
 #   use_issues_button: true
 #   use_repository_button: true
 #   use_edit_page_button: true
-#   extra_navbar: |
-#     Theme by <a href="https://projectpythia.org">Project Pythia</a>.<br>
-#     All code in Pythia Foundations is licensed under Apache 2.0. All other non-code content is licensed under <a href="https://creativecommons.org/licenses/by/4.0/">Creative Commons BY 4.0 (CC BY 4.0)</a>.
 #   extra_footer: |
 #     <img src="/_static/footer-logo-nsf.png" style="float:left;width:60px;height:60px;margin-right:1rem;">
 #     This material is based upon work supported by the National
 #     Science Foundation under Grant Nos. 2026863 and 2026899. Any
 #     opinions, findings, and conclusions or recommendations expressed
 #     in this material are those of the author(s) and do not necessarily
-#     reflect the views of the National Science Foundation.
+#     reflect the views of the National Science Foundation.<br><br>
+#     Theme by <a href="https://projectpythia.org">Project Pythia</a>.<br>
+#     All code in Pythia Foundations is licensed under Apache 2.0. All other non-code content is licensed
+#     under <a href="https://creativecommons.org/licenses/by/4.0/">Creative Commons BY 4.0 (CC BY 4.0)</a>.
 
 sphinx:
   config:
@@ -115,8 +115,6 @@ sphinx:
         binderhub_url: https://mybinder.org
         notebook_interface: jupyterlab
       extra_navbar: |
-        Theme by <a href="https://projectpythia.org">Project Pythia</a>.<br><br>
-        All code in Pythia Foundations is licensed under Apache 2.0. All other non-code content is licensed under <a href="https://creativecommons.org/licenses/by/4.0/">Creative Commons BY 4.0 (CC BY 4.0)</a>.<br><br>
         We want your feedback! Fill out this <a href="https://docs.google.com/forms/d/e/1FAIpQLSeVa1TC9xM-dk7qIE2e8bsgSrIP82yYDNw3wew3J46eREJa4w/viewform?usp=sf_link">Google Form</a>
         or see our <a href="https://foundations.projectpythia.org/appendix/how-to-contribute.html">Contributor's Guide</a>.
       logo_link: https://projectpythia.org

_templates/footer-extra.html

@@ -1,5 +1,14 @@
 <div class="container-fluid footer-extra">
   <div class="container">
+    <center>
+      Theme by <a href="https://projectpythia.org">Project Pythia</a>. All code
+      in Pythia Foundations is licensed under Apache 2.0. All other non-code
+      content is licensed under
+      <a href="https://creativecommons.org/licenses/by/4.0/">
+        Creative Commons BY 4.0 (CC BY 4.0)</a
+      >.
+    </center>
+    <br /><br />
     <div class="row">
       <p class="m-0">
         <img