Add Unit Test For - Trie search string

### 👽 What is required?
Function to test: `search();`
The algorithm is here : [Trie](https://github.com/knaxus/problem-solving-javascript/tree/master/src/_DataStructures_/Trees/Trie)

- Follow the ESLint rules strictly
- Follow the filename and folder structure strictly
- Since the Contribution Guide is not ready yet, go through the codebase pattern and add tests accordingly

Thank You!