Creating a Rider Plugin for external program execution

Hello guys,

While working in some projects before build the project I need to write a source with a specific extension (lets say ".mg") and then convert it using an external executable (let's say java -jar <MyJar> <input_file_mg> <output_file>)

Now, instead of having to execute from the terminal each time this command I would like to create a Plugin.
This plugin should create a custom action in the "right click menu" of all the files named "*.mg" and, on action execution, the command aforementioned should be called with the selected file path as input.

Is this possible?
I managed to launch the default plugin using https://blog.jetbrains.com/dotnet/2019/02/14/writing-plugins-resharper-rider/ but i can't find any reference to my problem in the documentation

thanks.