Add support for specifying comment types

[alex1989hu]

Using mycila/license-maven-plugin gives the possibility to maintain one LICENSE file in the repository and the plugin is able to apply it onto several file types.

In that way, I am not enforced to use one style of comment; I can apply license text onto XML and YAML files, too.

Also it is possible to configure file type and comment type. For example, I can configure the plugin the following way:

• files ends with .foo shall be handled as XML
• Dockerfile shall be handled as shell script etc.

Further details: https://github.com/mycila/license-maven-plugin#supported-comment-types

[andrewrynhard]

This is an interesting idea. This would be one of the only ways we could really support a license file on multiple types of files 🤔 .