feat: Add a new hanging protocol @ohif/mn (#3305)

* feat: Add a new hanging protocol @ohif/mn

* Add @ohif/seg example

* PR comments and a couple more fixes to make things cleaner

* PR comment

* Added an example to cause the PR checks to rerun

extensions/test-extension/src/custom-attribute/numberOfDisplaySetsWithImages.ts

@@ -1,5 +0,0 @@
-export default (study, extraData) => {
-  const ret = extraData?.displaySets?.filter(ds => ds.numImageFrames>0)?.length;
-  console.log("number of display sets with images", ret);
-  return ret;
-};

extensions/test-extension/src/custom-attribute/seriesDescriptionsFromDisplaySets.ts

@@ -1 +0,0 @@
-export default (study, extraData) => extraData?.displaySets?.map(ds => ds.SeriesDescription);