📚 DOCS: Fix deprecated import (#150)

Author: firasm

README.md

@@ -43,8 +43,8 @@ with and without plugins and features:
 
 ```python
 from markdown_it import MarkdownIt
-from markdown_it.extensions.front_matter import front_matter_plugin
-from markdown_it.extensions.footnote import footnote_plugin
+from mdit_py_plugins.front_matter import front_matter_plugin
+from mdit_py_plugins.footnote import footnote_plugin
 
 md = (
     MarkdownIt()
@@ -68,6 +68,10 @@ A footnote [^1]
 """)
 tokens = md.parse(text)
 html_text = md.render(text)
+
+## To export the html to a file, uncomment the lines below:
+# from pathlib import Path
+# Path("output.html").write_text(html_text)
 ```
 
 ### Command-line Usage