In the spirit of being minimally viable you could just have that in the filename and sort it before generating.
Since RSS is a pretty simple format, it doesn't require any automation, just a little copy and paste. "Handwriting your RSS feed"[0] makes the case for doing it that way.
1- I'm leaning towards an automatically generated file containing metadata, TOML or such
2- RSS is definitely coming, but is dependent on point 1 :-)