settings_sbt added

[ankitguptag18]

Hope this will solve issue #3 and we can use it as follows.

As per the documentation the committed code should create an environment variable INPUT_SETTINGS_SBT which would be available in entrypoint.sh

  id: sbt
  uses: lokkju/github-action-sbt@master
  with:
    commands: test
    settings_sbt: |
      externalResolvers += "maven-releases" at "https://${{secrets.NEXUS_REGISTRY}}/repository/maven-releases/",
      credentials += Credentials("Sonatype Nexus Repository Manager", "${{secrets.NEXUS_REGISTRY}}", "${{secrets.NEXUS_USERNAME}}", "${{secrets.NEXUS_PASSWORD}}")

[ankitguptag18]

@lokkju Hope you have time to look at the changes and if everything in place, maybe make a release so that we can use your action to authenticate against external repositories. :)