[Vuejs]-How to add OAuth github authentication to VueJS App

From the GitHub API page

Note: GitHub’s OAuth implementation supports the standard authorization code grant type. You should implement the web
application flow described below to obtain an authorization code and
then exchange it for a token. (The implicit grant type is not
supported.)

To do what you want to do you need a OAuth implementation that supports implicit grant type. But GitHub doesn’t support this so you need a "backend" like for example Express.