The documentation for Mojo's Maven Plugin for GWT is here: https://gwt-maven-plugin.github.io/gwt-maven-plugin/
NOTICE There is a new plugin (archetypes and eclipse integration), a fresh start
that correctly support multi-module projects, it is not version-bounded with GWT, support multiples GWT versions and
other fixes, improvements and best practices. This plugin is now considered the
legacy GWT maven plugin (aka mojo
GWT maven plugin) and the new one is considered the
new generation GWT maven plugin (aka tbroyer GWT maven
plugin). The legacy maven plugin is still supported but it is strongly encouraged to use the new one for new projects.