Because the error Unsupported content type in editor
I preffered just to rename the file like my-plugin.xml and to rename it after when I construct the packaging (with maven assembly) like this:
<files>
<file>
<source>${project.basedir}/my-plugin.xml</source>
<outputDirectory>/</outputDirectory>
<destName>plugin.xml</destName>
</file>
</files>
It is more a workaround but that way I can have the proper highlighting during the edition and proper name when deployed.