Fix container image building procedure in the CI/CD configuration

This MR fixes the CI/CD configuration that builds the container image.

See merge request pmpl/sonar-scanner-cli-image!6

This reverts commit da2657b1.

Fix shellcheck installation in the container image

This MR fixes `shellcheck` installation in the container image. It also adds
usage instructions of the container image.

Closes #4, #7.

See merge request pmpl/sonar-scanner-cli-image!5

Create GitLab CI/CD configuration

Closes #3

See merge request pmpl/sonar-scanner-cli-image!4

Add shellcheck

Closes #6 and #5

See merge request pmpl/sonar-scanner-cli-image!3

Closes #15.

Create build script for building container image

This MR adds a build script for building container image.

Close #2.

See merge request pmpl/sonar-scanner-cli-image!2

Create Dockerfile for building the container image

This MR provides a MVP Dockerfile for building the container image.

Closes #1.

See merge request pmpl/sonar-scanner-cli-image!1