✏️ Fix small typos in docs for developing extensions

docs/source/developer/extension_dev.rst

@@ -208,7 +208,7 @@ specific patch release of one of the core JupyterLab packages you can
 temporarily pin that requirement to a specific version in your own
 dependencies.
 
-If you must install a extension into a development branch of JupyterLab, you have to graft it into the source tree of JupyterLab itself. This may be done using the command
+If you must install an extension into a development branch of JupyterLab, you have to graft it into the source tree of JupyterLab itself. This may be done using the command
 
 ::
 

docs/source/developer/extension_points.rst

@@ -72,7 +72,7 @@ After a command has been added to the application command registry
 you can add them to various places in the application user interface,
 where they will be rendered using the metadata you provided.
 
-For example, you can add a button the Notebook toolbar to run the command with the ``CommandToolbarButtonComponent``.
+For example, you can add a button to the Notebook toolbar to run the command with the ``CommandToolbarButtonComponent``.
 
 Add a Command to the Command Palette
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^