Docs: Add compatibility and engine requirements

Author: snatalenko

README.md

@@ -11,6 +11,7 @@ Declarative Mapper for Node.js
 
 - [Overview](#overview)
   - [Quick Start Example](#quick-start-example)
+  - [Compatibility](#compatibility)
 - [Mapping Instructions](#mapping-instructions)
   - [Runtime Variables Quick Reference](#runtime-variables-quick-reference)
   - [Objects](#objects)
@@ -74,6 +75,11 @@ const mapper = createMapper({
 const results = sourceOrders.map(mapper); 
 ```
 
+## Compatibility
+
+- **Node.js:** 16+
+- **Browser:** best effort support; requires a `vm` polyfill
+
 ## Mapping Instructions
 
 In mapping JSON, the left side is a key in the resulting object.

package.json

@@ -20,6 +20,9 @@
     "typescript"
   ],
   "type": "module",
+  "engines": {
+    "node": ">=16"
+  },
   "main": "dist/cjs/index.js",
   "types": "types/index.d.ts",
   "exports": {