Only report new todo's, not existing todo's in files that changed

[ruudk]

Let's say you have a todo in a file that is in the main branch.

You now create a new branch, and modify that file, and make some changes without touching the todo.

On the PR, it will now comment that you have a todo in that file.

Is that expected? I think not.

In my opinion it should ignore existing todo's that are in the base branch.

[gkampitakis]

Hey 👋 thanks for opening this issue and all the prs and discussions. I would swear this is already how this works #9. Maybe there is a weird edge case?