The way I like to make changes in response to a PR review is to make any fixes to the original commits using a rebase. I don't want commits that "fix typos" in my history, especially at the feature branch level. There are varying opinions and approaches to this, but I think rebasing is great tool when used on your own branches and in moderation.
Standard procedure for this is - 1) Make the code change; 2) Commit the change; 3) Start an interactive rebase; 4) Identify the commit that needs fixing; 5) Move the new commit underneath it; 6) Change it to "squash". It's quite tedious.
Fixup commits are created using git commit --fixup <SHA>. Practically, --fixup associates a new commit with an existing commit so that when you do an interactive rebase, you don't have to re-order any commits in order to squash them. And you don't have to change any commit messages. From the docs:
--autosquash is a flag to use with rebase and takes everything a step further. Once you've committed your changes with git commit --fixup <SHA> you can start an interactive rebase as normal, but pass the --autosquash flag too.