docs: document minimum node version requirement (#60)

Author: Fyko

README.md

@@ -16,6 +16,7 @@ const decoded = encoder.decode(encoded);
 ```
 
 ## Platform support
+⚠ Node.js 12.0.0 or newer is required.
 
 - Linux x64 & ia32
 - Linux arm (RPi 1 & 2)

package.json

@@ -39,6 +39,9 @@
 	"eslintConfig": {
 		"extends": "aqua/node"
 	},
+	"engines": {
+		"node": ">=12.0.0"
+	},
 	"binary": {
 		"module_name": "opus",
 		"module_path": "./prebuild/{node_abi}-napi-v{napi_build_version}-{platform}-{arch}-{libc}-{libc_version}/",