Single-source the version number.

This shouldn't be duplicated in `conf.py`.

Author: rwb27

docs/source/conf.py

@@ -1,5 +1,6 @@
 import logging
 import labthings_fastapi
+import importlib.metadata
 
 # Configuration file for the Sphinx documentation builder.
 #
@@ -12,7 +13,7 @@
 project = "labthings-fastapi"
 copyright = "2024, Richard Bowman"
 author = "Richard Bowman"
-release = "0.0.10"
+release = importlib.metadata.version("labthings-fastapi")
 
 # -- General configuration ---------------------------------------------------
 # https://www.sphinx-doc.org/en/master/usage/configuration.html#general-configuration