66.fetchBranchNames

Write a function named fetchBranchNames that receives 2 parameters:

• the username of a GitHub user
• the name of a public repository owned by the user above - repo

The function should return a Promise that resolves to an Array with the names of all branches in that repository.

If the username or repo does not exist, the returned Promise should resolve to an empty Array.

PS: here's the link to the GitHub API: https://docs.github.com/en/rest. It's your job to find the correct endpoint to call.