Allow parametrisation of Doxia parser per file

Currently only the attributes used for rendering the site can be parameterized in https://maven.apache.org/plugins/maven-site-plugin/site-mojo.html#attributes. There is no possibility to configure the parser in https://github.com/apache/maven-doxia-sitetools/blob/dacaa552c1b8e89eed84db0f43b6b0a72be91d0c/doxia-site-renderer/src/main/java/org/apache/maven/doxia/siterenderer/DefaultSiteRenderer.java#L322 per document.

This would be nice in the context of https://issues.apache.org/jira/browse/DOXIA-722 where generation of anchors should be switched on/off for certain documents. Also generation of comments may be desirable for certain documents.

I propose the following additional plugin goal parameter:

<parserConfigurations>
  <parserConfiguration>
    <patterns>
      <pattern>**/apt/**</pattern>
    </patterns>
    <emitAnchorsForIndexableEntries>false</emitAnchorsForIndexableEntries>
    <emitComments>true</emitComments>
  </parserConfiguration>
<parserConfigurations>

where parserConfigurations is an array of a complex type with (include) patterns on the source path (String array) and boolean methods for features.

This also required an upgrade to Maven Plugin Tools 3.13.0.