add include-markdown plugin

README.md

@@ -87,8 +87,9 @@ For the extensions:
 
 For the plugins:  
 `pip install mkdocs-minify-plugin`  
-`pip install mkdocs-macros-plugin`
-`pip install mkdocs-embed-external-markdown`
+`pip install mkdocs-macros-plugin`  
+`pip install mkdocs-embed-external-markdown`  
+`pip install mkdocs-include-markdown-plugin`  
 `pip install mkdocs-table-reader-plugin`
 
 ##### Conda