Move CLI crate to root of workspace

Somehow I missed that this was a thing you could do? It's a much
cleaner organization, and it makes it so that you don't have to
explicitly specify the crate to build.

build.rs

@@ -0,0 +1,7 @@
+fn main() {
+    cynic_codegen::register_schema("startgg")
+        .from_sdl_file("schema/startgg.graphql")
+        .unwrap()
+        .as_default()
+        .unwrap();
+}