updated readme

README.md

@@ -101,7 +101,7 @@ In short, in the context of **by-node-env**, the environment variable `NODE_ENV`
 
 ## NODE_ENV
 
-By design, **by-node-env** needs to resolve `NODE_ENV` ahead of starting your application to select appropriate **scripts** in **package.json** for execution, at the same time set the resolved `NODE_ENV` as `process.env.NODE_ENV` in your application runtime.
+By design, **by-node-env** must resolve `NODE_ENV` ahead of starting your application to select appropriate **scripts** in **package.json** for execution, at the same time set the resolved `NODE_ENV` as `process.env.NODE_ENV` in your application runtime.
 
 The priority order of resolving `NODE_ENV` is as follows: