update docs Interface.js, abstract model layer errors

src/lib/errors.js

@@ -0,0 +1,13 @@
+import copy from '../copy/en'
+
+export function modelLayerGeneric (parts) {
+  return new Error(copy.errors.modelLayer(parts))
+}
+
+export function noFragment (parts) {
+  return new Error(copy.errors.noFragment(parts))
+}
+
+export function noResource (parts) {
+  return new Error(copy.errors.noResource(parts))
+}