2) Find the CSV file you want to load in GitHub and click the 'Raw' button to get the URL to the raw CSV file. Take a copy of this URL BUT remove the token=XXXXX part at the end.
3) In Qlik Sense, create a REST connection using the URL from step 2).
4) In the connection dialog, add a Query header with name 'Authorization' and value 'token PERSONAL_ACCESS_TOKEN' where PERSONAL_ACCESS_TOKEN is the value from step 1).
You should now be able to save the connection and then select data from the underlying file. I tested this with an XML file but CSV should be the same. If this is a public repo you can likely skip step 1).