feat: keyword to prevent variables substitution

    * any [GitLab CI variable](https://docs.gitlab.com/ee/ci/variables/#predefined-environment-variables)

      (ex: `${CI_ENVIRONMENT_URL}` to retrieve the actual environment exposed route)

You can prevent any line from being processed by appending `# nosubst` at the end of the line. For instance in the following example, `${REMOTE_SERVICE_NAME}` won't be replaced by its environment value during GitLab job execution:

```yaml

apiVersion: v1

kind: ConfigMap

metadata:

  labels:

    app: ${APPLICATION_NAME}

  name: ${APPLICATION_NAME}

data:

  application.yml: |

    remote:

      some-service:

          name: '${REMOTE_SERVICE_NAME}' # nosubst

```

> :warning:

>

> In order to be properly replaced, variables in your YAML descriptors shall be written with curly braces (ex: `${MYVAR}` and not `$MYVAR`).

  }

  function awkenvsubst() {

    awk '{while(match($0,"[$]{[^}]*}")) {var=substr($0,RSTART+2,RLENGTH -3);val=ENVIRON[var];gsub(/["\\]/,"\\\\&", val);gsub("\n", "\\n", val);gsub("\r", "\\r", val);gsub("[$]{"var"}",val)}}1'

    awk '!/# *nosubst/{while(match($0,"[$]{[^}]*}")) {var=substr($0,RSTART+2,RLENGTH -3);val=ENVIRON[var];gsub(/["\\]/,"\\\\&", val);gsub("\n", "\\n", val);gsub("\r", "\\r", val);gsub("[$]{"var"}",val)}}1'

  }

  function exec_hook() {