Rename LabelNameGenerator to SegTemplateEditor

This PR adds the metadata for a new 3D Slicer extension: **SegTemplateEditor**

- Replaces previous `LabelNameGenerator` name
- New repository: https://github.com/esheo-skia/Slicer-SegTemplateEditor
- Category: Segmentation

Author: esheo-skia

LabelNameGenerator.json renamed to SegTemplateEditor.json

@@ -4,6 +4,6 @@
   "build_subdirectory": ".",
   "category": "Segmentation",
   "scm_revision": "main",
-  "scm_url": "https://github.com/esheo-skia/Slicer-LabelNameGenerator.git",
+  "scm_url": "https://github.com/esheo-skia/Slicer-SegTemplateEditor.git",
   "tier": 1
 }