Create sidebar version info section

Contains the version string and the date updated.

src/technote/config.py

@@ -644,6 +644,11 @@ def date_updated_iso(self) -> Optional[str]:
         else:
             return None
 
+    @property
+    def version(self) -> Optional[str]:
+        """The version, as a string if available."""
+        return self.toml.technote.version
+
     def set_content_title(self, title: str) -> None:
         """Set the title from the content nodes."""
         self._content_title = title

src/technote/theme/components/sidebar-version.html

@@ -1,5 +1,15 @@
 <section class="technote-sidebar-section">
+  <h2 class="technote-sidebar-section__heading">Version</h2>
+
+  {% block version %}
+  {% if technote.version %}
+    <p class="technote-sidebar-version__version"><span class="technote-sidebar-version__label">Version</span> <span class="technote-sidebar-version__value">{{technote.version}}</span></p>
+  {% endif %}
+  {% endblock version %}
+
+  {% block date_updated %}
   {% if technote.date_updated_iso %}
-    <time datetime="technote.date_updated_iso">{{ technote.date_updated_iso }}</time>
+    <p class="technote-sidebar-version__date"><span class="technote-sidebar-version__label">Updated</span> <time class="technote-sidebar-version__value" datetime="technote.date_updated_iso">{{ technote.date_updated_iso }}</time></p>
   {% endif %}
+  {% endblock date_updated %}
 </section>