[shfmt] Add target for installing new package

[shfmt] Add target for installing new package (#37)

* feat(install/Makefile): add target which installs new package (shfmt)

* feat(shellcheck): add new target which installs shellcheck

* fix(README): regenerate README.md

* fix(install/Makefile): parameterize OS

* refactor(install/Makefile): sort dependencies alphabetically

* Merge shellcheck in shfmt