Is there a terminal provided for remote repository on GitHub or GitLab website? Just like we can change a file and commit the changes in the website.
I am a React developer and not happy with cloning a heavy repository just for npm run build.
I don't expect this functionality exists but it's just a little hope.
Thanks!

Gitlab offers a full featured web IDE for inline repository files editing.
Please look at the following screenshot:
Edit
Here is a screenshot about the terminal activation button.