feat: lesion-tracker extension (#1420)

* chore: init lesion-tracker extension

* chore: dev build for lesion-tracker extension

* fix: a more appropriate library name

* chore: fix script naming

extensions/lesion-tracker/README.md

@@ -0,0 +1,38 @@
+# @ohif/extension-lesion-tracker
+
+This project is an OHIF extension that can be used with the Core OHIF Platform,
+either at runtime, or as an ES6 dependency, to create a medical image viewing
+application similar to that of the [legacy Lesion
+Tracker][legacy-lesion-tracker] viewer.
+
+## About
+
+...
+
+## Scope
+
+...
+
+### Configuration
+
+...
+
+### Extensions
+
+...
+
+## Build & Deploy
+
+...
+
+## Funding/Support
+
+...
+
+<!--
+  LINKS
+  -->
+
+<!-- prettier-ignore-start -->
+[legacy-lesion-tracker]: http://lesiontracker.ohif.org/studylist
+<!-- prettier-ignore-end -->