Support Mule 4 (Anypoint Studio 7)

[NoxHarmonium]

When running the image extract tools over Anypoint Studio 7, errors like the following occur:

$ lein run -- -d /mnt/c/Tools/AnypointStudio-7/ -o test/images extract-images
Warning: Image file [ images:/canvas/flow.png ] not found in [ #object[java.io.File 0x71166348 /mnt/c/Tools/AnypointStudio-7/plugins/org.mule.tooling.ui.modules.core_7.3.5.201909031748.jar] ]
Warning: Image file [ images:/canvas/set-payload.png ] not found in [ #object[java.io.File 0x71166348 /mnt/c/Tools/AnypointStudio-7/plugins/org.mule.tooling.ui.modules.core_7.3.5.201909031748.jar] ]
Warning: Image file [ images:/canvas/raise-error.png ] not found in [ #object[java.io.File 0x71166348 /mnt/c/Tools/AnypointStudio-7/plugins/org.mule.tooling.ui.modules.core_7.3.5.201909031748.jar] ]

The metadata extractor needs to be able to follow these images:/ urls.

[NoxHarmonium]

Seems like a URL starting with the images:/ prefix are referring to org.mule.tooling.images_*.jar
It shouldn't be too difficult to put in a special case mapping for this.