This extension has two stages.
In the first stage it checks whether a newly opened tab is a secure YouTube site (https://www.youtube.com or https://youtube.com). If it is not, it does nothing, and that's it.
In the second stage ie. if it is a secure YouTube site, all it does is the following:
// Prints this comment to console
console.log('search focused by extension')
// Finds the first <input> element with id="search", and focuses it so you can
// immediately start typing.
document.querySelector('input#search').focus()
The extension needs no additional permissions, nor does it collect any data.