restructure headings

doc/index.rst

@@ -9,16 +9,22 @@
 Content
 #######
 
+User Documentation
+==================
+
 .. toctree::
    :maxdepth: 1
    :caption: User Documentation
 
-   user/installation
-   user/methods
-   user/printers
-   user/raspi
-   user/usage
-   user/barcode
+   user/installation.rst
+   user/methods.rst
+   user/printers.rst
+   user/raspi.rst
+   user/usage.rst
+   user/barcode.rst
+
+Printer profiles
+================
 
 .. toctree::
    :maxdepth: 1
@@ -28,30 +34,36 @@ Content
    printer_profiles/available-profiles.rst
    printer_profiles/available-encodings.rst
 
+Developer Documentation
+=======================
+
 .. toctree::
    :maxdepth: 1
    :caption: Developer Documentation
 
-   dev/release-process
-   dev/contributing
-   dev/changelog
-   dev/todo
+   dev/release-process.rst
+   dev/contributing.rst
+   dev/changelog.rst
+   dev/todo.rst
+
+API Documentation
+=================
 
 .. toctree::
    :maxdepth: 1
    :caption: API Documentation
 
-   api/escpos
-   api/printer
-   api/constants
-   api/exceptions
-   api/capabilities
-   api/config
-   api/image
-   api/cli
-   api/magicencode
-   api/codepages
-   api/katakana
+   api/escpos.rst
+   api/printer.rst
+   api/constants.rst
+   api/exceptions.rst
+   api/capabilities.rst
+   api/config.rst
+   api/image.rst
+   api/cli.rst
+   api/magicencode.rst
+   api/codepages.rst
+   api/katakana.rst
 
 ##################
 Indices and tables