Don't encourage users to change system directory ownership

From `README.md`:

> If you get a permission denied error, maybe you need to give yourself access to the install folder via `sudo chown -R $(whoami) /usr/local/bin`.

I really don't think it's a good idea to encourage users to change ownership of system directories. Instead, I propose either installing `kitty` in `/usr/local/bin` using `sudo`, or install it in `~/.local/bin` instead. I think the latter is the better option, assuming only a single user needs to have it installed.