[feat] Additional Compatibility and Dependency Requirements

Following up on #25, I identified some additional requirements to improve compatibility and reduce dependencies. Here are the proposed changes: 1. Avoid using `tput` to eliminate the dependency on `ncurses` 2. Avoid negative length specifications on string expansion, which was introduced in Bash 4.2[1][negative_index]. This may allow ell to be run on Bash 4.1 3. Explicit declaration of optional dependency on `util-linux` Additionally, `coreutils` as an implicit dependency, including commands such as `cat`, `sleep`, `rm`, and `mktemp`, is widely available on Linux and have equivalents on OS X. No further compatibility issues have been identified as of now. However, ongoing efforts are needed to further adjust the script to make it POSIX compliant. [negative_index]: https://git.savannah.gnu.org/cgit/bash.git/tree/CHANGES?h=bash-4.2&id=495aee441b75276e38c75694ccb455bb6463fdb9#n341