add support for env schema, allowing users to provide environment variables for an application

test/data/valid/mixed.json

@@ -0,0 +1,13 @@
+{
+  "text": {
+    "description": "Default text property",
+    "type": "string"
+  },
+  "/hello": {
+    "text": {
+      "description": "Welcome message",
+      "type": "string",
+      "required": true
+    }
+  }
+}