Initial Backstage setup

plugins/README.md

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+# The Plugins Folder
+
+This is where your own plugins and their associated modules live, each in a
+separate folder of its own.
+
+If you want to create a new plugin here, go to your project root directory, run
+the command `yarn new`, and follow the on-screen instructions.
+
+You can also check out existing plugins on [the plugin marketplace](https://backstage.io/plugins)!