Corrected a typo

Enevevet · web-flow · commit 95115b67e45b · 2021-10-26T10:33:48.000+02:00
diff --git a/advanced/extensions.rst b/advanced/extensions.rst
@@ -4,7 +4,7 @@
 Custom Extensions
 #################
 
-**This page is uncer construction**
+**This page is under construction**
 
 See the :ref:`custom-component` section for an example of building
 custom extensions to MathJax.
