cmd/msrfetch: save enriched compound data

This implementation of cmd/msrfetch is only temporary, used to fetch the
testdata. At this point we have all metadata present in the repo and all
that is left is to fetch the media.

Signed-off-by: Yonah <contrib@gensokyo.uk>

.gitignore

@@ -5,7 +5,7 @@
 *.so
 *.dylib
 *.pkg
-/monstersirenfetch
+/msrfetch
 
 # Test binary, built with `go test -c`
 *.test