You could, but then you will have to continuously monitor the main branch and pull in updates if you want new features, bug fixes, security updates etc., and possibly you'll need to deal with merge conflicts.
You might also need custom release, install, and upgrade tooling for your fork. And if there are bugs in anything that has diverged, it will be up to you to fix those yourself.
1) Clone the latest version of the tool
2) Apply the patches needed for this feature
3) Profit.
Or is there some reason why the change has to live in the "main" branch for the official project on github?