Added documentation on migration

docs/getting-started.md

@@ -32,7 +32,7 @@ pip install mkdocs && mkdocs --version
 
 !!! warning "MkDocs version requirements"
 
-    As of 2.0, Material requires MkDocs >= 0.17.1
+    Material requires MkDocs >= 0.17.1
 
   [2]: http://www.mkdocs.org
 
@@ -469,6 +469,23 @@ automatically included.
 
   [22]: https://disqus.com
 
+## Migration
+
+### From 1.x to 2.0
+
+Material for MkDocs 2.0 requires MkDocs 0.17.1, as this version introduced
+changes to the way themes can define options. The following variables inside
+your project's `mkdocs.yml` need to be renamed:
+
+* `extra.feature` becomes `theme.feature`
+* `extra.palette` becomes `theme.palette`
+* `extra.font` becomes `theme.font`
+* `extra.logo` becomes `theme.logo`
+
+Localization is now separate in theme language and search language. While
+there can only be a single language on theme-level, the search supports
+multiple languages which can be separated by commas.
+
 ## Extensions
 
 MkDocs supports several [Markdown extensions][23]. The following extensions