Expand README content, split into multiple files

Signed-off-by: Solomon Hykes <sh.github.6811@hykes.org>

doc/tutorials.md

@@ -0,0 +1,15 @@
+# Dagger Tutorials
+
+## Compute a test configuration
+
+Currently `dagger` can only do one thing: compute a configuration with optional inputs, and print the result.
+
+If you are confused by how to use this for your application, that is normal: `dagger compute` is a low-level command
+which exposes the naked plumbing of the Dagger engine. In future versions, more user-friendly commands will be available
+which hide the complexity of `dagger compute` (but it will always be available to power users, of course!).
+
+Here is an example command, using an example configuration:
+
+```
+$ dagger compute ./examples/simple --input-string www.host=mysuperapp.com --input-dir www.source=.
+```