[Docs] Various fixes (#2136)

* [Docs] Various fixes

* More fixes

* Fix ADRs

* Typo

docs/plugins/create-a-plugin.md

@@ -15,20 +15,16 @@ dependencies, then run the following on your command line (invoking the
 yarn create-plugin
 ```
 
-<p align='center'>
-    <img src='https://github.com/spotify/backstage/raw/master/docs/getting-started/create-plugin_output.png' width='600' alt='create plugin'>
-</p>
+![](../assets/getting-started/create-plugin_output.png)
 
 This will create a new Backstage Plugin based on the ID that was provided. It
 will be built and added to the Backstage App automatically.
 
-_If `yarn start` is already running you should be able to see the default page
-for your new plugin directly by navigating to
-`http://localhost:3000/my-plugin`._
+> If `yarn start` is already running you should be able to see the default page
+> for your new plugin directly by navigating to
+> `http://localhost:3000/my-plugin`.
 
-<p align='center'>
-    <img src='https://github.com/spotify/backstage/raw/master/docs/plugins/my-plugin_screenshot.png' width='600' alt='my plugin'>
-</p>
+![](../assets/my-plugin_screenshot.png)
 
 You can also serve the plugin in isolation by running `yarn start` in the plugin
 directory. Or by using the yarn workspace command, for example:
@@ -40,7 +36,3 @@ yarn workspace @backstage/plugin-welcome start # Also supports --check
 This method of serving the plugin provides quicker iteration speed and a faster
 startup and hot reloads. It is only meant for local development, and the setup
 for it can be found inside the plugin's `dev/` directory.
-
-[Next Step - Structure of a plugin](structure-of-a-plugin.md)
-
-[Back to Getting Started](../README.md)