Factor out contributing file

@@ -0,0 +1,14 @@
+### Contributing
+
+We welcome suggestions to this reading list.
+
+In the [issues](https://github.com/mmcgrana/services-engineering/issues)
+for this repository we track both specific suggestions for additions
+as well as topics that we'd like to cover don't have good resources
+for yet. Please make your own suggestions by opening an issue or
+commenting on an existing one. We've already incorporated many good
+suggestions from early readers of this list!
+
+Note that the list only includes material that's been read
+personally by the editor, so some suggestions may have a long
+turnaround time, especially books.

@@ -1,8 +1,9 @@
 ## Services Engineering Reading List
 
-* A reading list for services engineering, with a focus on cloud infrastructure services
-* Most content is on applied distributed systems and systems operations
-* Please send suggestions to [@mmcgrana](https://twitter.com/mmcgrana) or [open an issue](https://github.com/mmcgrana/services-engineering/issues)
+We welcome [suggestions](CONTRIBUTING.md).
 
 #### Papers