Rename immersive scale submodule and update reference

The submodule had the same name as the actual module when
installed, which was causing issues when installing immersive
scaler after installing cats dev. See triazo/immersive_scaler#12

.gitmodules

@@ -1,3 +1,3 @@
 [submodule "extern_tools/immersive_scaler"]
-	path = extern_tools/immersive_scaler
+	path = extern_tools/imscale
 	url = git@github.com:triazo/immersive_scaler.git

__init__.py

@@ -65,8 +65,8 @@
 if not is_reloading:
     # This order is important
     import mmd_tools_local
-    if find_spec("immersive_scaler") and find_spec("immersive_scaler.immersive_scaler"):
-        import immersive_scaler.immersive_scaler as imscale
+    if find_spec("imscale") and find_spec("imscale.immersive_scaler"):
+        import imscale.immersive_scaler as imscale
     from . import updater
     from . import tools
     from . import ui
@@ -291,8 +291,8 @@ def register():
         print('mmd_tools is already registered')
 
     # Register immersive scaler if it's loaded
-    if find_spec("immersive_scaler") and find_spec("immersive_scaler.immersive_scaler"):
-        import immersive_scaler.immersive_scaler as imscale
+    if find_spec("imscale") and find_spec("imscale.immersive_scaler"):
+        import imscale.immersive_scaler as imscale
         try:
             imscale.register()
         except ModuleNotFoundError:
@@ -374,8 +374,8 @@ def unregister():
         pass
 
     # Unload immersive scaler
-    if find_spec("immersive_scaler") and find_spec("immersive_scaler.immersive_scaler"):
-        import immersive_scaler.immersive_scaler as imscale
+    if find_spec("imscale") and find_spec("imscale.immersive_scaler"):
+        import imscale.immersive_scaler as imscale
         try:
             imscale.unregister()
         except ModuleNotFoundError:

ui/scale.py

@@ -20,11 +20,13 @@ def check_for_imscale():
 
     draw_imscale_ui = None
 
-    if find_spec("immersive_scaler") and find_spec("immersive_scaler.immersive_scaler"):
-        import immersive_scaler.immersive_scaler as imscale
+    # Check if using immersive scaler shipped with cats
+    if find_spec("imscale") and find_spec("imscale.immersive_scaler"):
+        import imscale.immersive_scaler as imscale
         draw_imscale_ui = imscale.ui.draw_ui
         return
 
+    # Check if it's present in blender anyway (installed separately)
     for mod in addon_utils.modules():
         if mod.bl_info['name'] == "Immersive Scaler":
             # print(mod.__name__, mod.bl_info['version'])