Slack channel from configs doesn't work when using token

[rdeaconu]

Hi, thanks for putting together this plugin!

I am trying to use a Slack token for this passed through env vars while specifying the Slack channel through the configs. However this doesn't seem to work, I am seeing this error message:

A Slack Channel must be created and set in the SLACK_CHANNEL environment variable on your CI environment.
Please make sure to set a Slack Channel in the SLACK_CHANNEL environment variable on your CI environment. Alternatively, provide slackChannel as a configuration option.

This is the configuration of my plugin:

[
    "semantic-release-slack-bot",
    {
        "notifyOnSuccess": false,
        "notifyOnFail": false,
        "markdownReleaseNotes": true,
        "slackChannel": "#alerts",
        "branchesConfig": [
            {
                "pattern": "dev",
                "notifyOnSuccess": true,
                "onSuccessTemplate": {
                    "blocks": [
                        {
                            "type": "section",
                            "text": {
                                "type": "mrkdwn",
                                "text": "A new version has been released to *development*! :rocket:"
                            }
                        },
                        {
                            "type": "divider"
                        },
                        {
                            "type": "section",
                            "text": {
                                "type": "mrkdwn",
                                "text": "$release_notes"
                            }
                        }
                    ]
                }
            }
        ]
    }
]

I would expect the configuration to work when passing the Slack token as env var, is that not the case?