Add basic dev docs

Author: jeromekelleher

docs/development.rst

@@ -4,4 +4,18 @@
 Developer documentation
 =======================
 
-.. todo:: Write developer documentation.
+All contributions, bug reports, documentation improvements and ideas are welcome. If you
+think there is anything missing, please open an
+`issue <https://github.com/tskit-dev/tsinfer/issues>`_ or
+`pull request <https://github.com/tskit-dev/tsinfer/pulls>`_ on GitHub.
+
+See the `tskit developer documentation <https://tskit.dev/tskit/docs/stable/development.html>`_
+for the general development workflow (git, prek, testing, documentation).
+
+Install development dependencies with::
+
+    uv sync
+
+Run the tests with::
+
+    uv run pytest