chore: updates readme

README-ru.md

@@ -10,6 +10,8 @@
 
 ## Установка
 
+Требуется Node.js 16 и выше.
+
 ```bash
 npm install @e22m4u/js-path-trie
 ```

README.md

@@ -10,6 +10,8 @@ a [prefix tree](https://en.wikipedia.org/wiki/Trie) (trie).
 
 ## Installation
 
+Node.js 16 or higher is required.
+
 ```bash
 npm install @e22m4u/js-path-trie
 ```