Allow to set the version of shellcheck when using the `check` job

[timobrembeck]

Describe Request:

At the moment, the check job just runs the version of shellcheck which is included in the CircleCI base image (which corresponds to the Ubuntu repository) and might quite outdated. Even when the default version of the install command is updated (#61/#62), the check job would not benefit from this, since install is not called here.

Examples:

version: '2.1'
orbs:
  shellcheck: circleci/[email protected]
workflows:
  my_workflow:
    jobs:
      - shellcheck/check:
          dir: ./myScripts
          version: 0.9.0

[marboledacci]

What is the purpose of this?, you can install an specific version and then do the check.