Consider to remove Makefile?

The `Makefile` is no longer required since we have implemented the script directive, see https://github.com/emacs-eask/cli/pull/69.

Replacement will look something like that in `Eask`-file.

```elisp
(script "clean" "eask clean all")
(script "lint-checkdoc" "eask lint checkdoc --strict")
(script "lint-package" "eask lint package")
```