Update configuration.md

2019 replaced by 2020 in line 94.

docs/configuration.md

@@ -91,7 +91,7 @@ heading_anchors: true
 # appears at the bottom of every page's main content
 # Note: The footer_content option is deprecated and will be removed in a future major release. Please use `_includes/footer_custom.html` for more robust
 markup / liquid-based content.
-footer_content: "Copyright &copy; 2017-2019 Patrick Marsceill. Distributed by an <a href=\"https://github.com/pmarsceill/just-the-docs/tree/master/LICENSE.txt\">MIT license.</a>"
+footer_content: "Copyright &copy; 2017-2020 Patrick Marsceill. Distributed by an <a href=\"https://github.com/pmarsceill/just-the-docs/tree/master/LICENSE.txt\">MIT license.</a>"
 
 # Footer last edited timestamp
 last_edit_timestamp: true # show or hide edit time - page must have `last_modified_date` defined in the frontmatter