You need a valid tsconfig that defines the scope of the project and it seems renovate’s tsconfig doesn’t meet this requirement. You can always --skip manually as an alternative option.
BTW the VSCode extension which someone else linked to discovered everything perfectly, which is another hint that your tool needs to improve, not your users.
Even if tsconfig.json was very important, and the users are all wrong and you're right, the only thing your readme says is: "The CLI will respect the tsconfig.json for loading source files." which is insufficient.