Fix #35322: Modernize javascript snippets

[prog-rajkamal]

This PR addresses #35322 by adding following snippets to javascript and javascriptreact languages:

// for loop (let) [useforl]
for (let index = 0; index < array.length; index++) {
    let element = array[index];
    
}

// For Of [use forof]
for (let iterator of object) {
    
}

[msftclas]

All CLA requirements met.

[mjbvz]

Thanks! Should be in the next insiders build