Associating a marketplace solution with a filetype requires you to declare it on your solution listing. It's only a matter of *adding one or more tags* of the form "fileExtension_xxx" to your entry, where "xxx" is the extension of the file your solution is supporting. For example, an extension adding an editor for Go files would have a "fileExtension_go" tag, and an extension adding an editor for Dockerfile files would have a "fileExtension_Dockerfile" tag. If your solution supports multiple file types, simply add multiple tags, one for each file type. Please set these as soon as possible, since this feature will become widely used once Neon is released. Being ready before the release will benefit users who are looking for good plugins, and will add to the popularity of your solution.
Xtext 2.10 released, Oomph setup and Target configs updated