v17: Default repository and activeProfile configuration

[zteater]

Maven Central is now an optional repository. Override this default configuration at repository.

- name: maven-settings-xml-action
  uses: whelk-io/maven-settings-xml-action@v17
  with:
    repositories: |
      [
        {
          "id": "some-repository",
          "name": "some-repository-name",
          "url": "http://some.repository.url",
          "releases": {
            "enabled": "true"
          },
          "snapshots": {
            "enabled": "false"
          }
        }
      ]

When repository is not configured, the following default is applied to settings.xml:

<profiles>
  <profile>
    <id>github</id>
    <repositories>
      <repository>
        <id>central</id>
        <name>Maven Central</name>
        <url>https://repo1.maven.org/maven2</url>
        <releases>
          <enabled>true</enabled>
        </releases>
        <snapshots>
          <enabled>false</enabled>
        </snapshots>
      </repository>
    </repositories>
    <pluginRepositories/>
  </profile>
</profiles>

github is now an optional activeProfile. Override this default activeProfile at active_profiles.

- name: maven-settings-xml-action
  uses: whelk-io/maven-settings-xml-action@v17
  with:
    active_profiles: |
      [ 
        "some-profile"
      ]

When active_profiles is not configured, the following default is applied to settings.xml:

<activeProfiles>
  <activeProfile>github</activeProfile>
</activeProfiles>

Updated README.md with local setup and contributing guidelines.

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This discussion was created from the release 17: Merge pull request #105 from whelk-io/develop.