Test script for grep

[vidyalakshmir]

Write tests to test the functionality of grep

[rishabhBudhouliya]

@vidyalakshmir After the resolution of: Lind-Project/lind-wasm#946
I've manually verified basic functionalities of grep work in lind-wasm

Here's a PR for the test script that does the same: #150

One open issue is grep -r, it fails right now.