Add extra information to plugin dev index

docs/source/dev/index.rst

@@ -5,14 +5,52 @@
 Since |Flake8| 2.0, the |Flake8| tool has allowed for extensions and custom
 plugins. In |Flake8| 3.0, we're expanding that ability to customize and
 extend **and** we're attempting to thoroughly document it. Some of the
-documentation in this section will reference third-party documentation
+documentation in this section may reference third-party documentation to
-to reduce duplication and to point you, the developer, towards
+reduce duplication and to point you, the developer, towards the authoritative
-the authoritative documentation for those pieces.
+documentation for those pieces.
+
+Getting Started
+===============
+
+To get started writing a |Flake8| :term:`plugin` you first need:
+
+- An idea for a plugin
+
+- An available package name on PyPI
+
+- One or more versions of Python installed
+
+- A text editor or IDE of some kind
+
+- An idea of what *kind* of plugin you want to build:
+
+  * Formatter
+
+  * Check
+
+Once you've gathered these things, you can get started.
+
+All plugins for |Flake8| must be registered via `entry points`_. In this
+section we cover:
+
+- How to register your plugin so |Flake8| can find it
+
+- How to make |Flake8| provide your check plugin with information (via
+  command-line flags, function/class parameters, etc.)
+
+- How to make a formatter plugin
+
+- How to write your check plugin so that it works with |Flake8| 2.x and 3.x
 
 .. toctree::
+    :caption: Plugin Developer Documentation
     :maxdepth: 2
 
-    cross_compatibility
-    plugin_parameters
     registering_plugins
+    plugin_parameters
     formatters
+    cross_compatibility
+
+
+.. _entry points:
+    https://setuptools.readthedocs.io/en/latest/pkg_resources.html#entry-points