Add Sphinx sprint details (#1450)

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

Author: AA-Turner

src/content/sprints/Sphinx.md

@@ -0,0 +1,24 @@
+---
+title: "Sphinx"
+numberOfPeople: "2-7"
+pythonLevel: "Any"
+contactPerson:
+  name: "Adam Turner"
+  email:
+  github: AA-Turner
+  twitter:
+links:
+  - title: "Sphinx website"
+    url: "https://www.sphinx-doc.org/"
+  - title: "Sphinx on GitHub"
+    url: "https://github.com/sphinx-doc/sphinx/"
+  - title: "Easy Issues"
+    url: "https://github.com/sphinx-doc/sphinx/issues?q=sort%3Aupdated-desc%20is%3Aissue%20is%3Aopen%20label%3Aeasy%2C%22help%20wanted%22"
+---
+
+Help us work on Sphinx, the documentation generator that powers Python, Linux,
+Jupyter, and more!
+
+We're very happy to have contributors new and old! We'd be interested in
+improvements to the documentation, core extensions, theme usability, and
+anything else you'd be keen to work on!