Associate jbosstools & devstudio marketplace entries by fileextension to file types opened in Eclipse

I need a list of file extensions we want associated with JBT/devstudio.

Then I can add those to the list of tags on the marketplace entries:

https://marketplace.eclipse.org/content/jboss-tools
https://marketplace.eclipse.org/content/red-hat-jboss-developer-studio

eg., for freemarker, we want to add tag = fileExtension_ftl [1]

ref: https://www.eclipse.org/eclipse/news/4.6/platform.php#text-editor-selection-strategy
ref: https://www.eclipse.org/community/eclipse_newsletter/2016/june/article1.php (see #5)

[1] https://marketplace.eclipse.org/content/freemarker-ide-jboss-tools

related: https://bugs.eclipse.org/bugs/show_bug.cgi?id=480176
related: https://bugs.eclipse.org/bugs/show_bug.cgi?id=494050