[Registry Preview] Adds application to Open with list for REG files (#26033)

* 25834

* Asociate Registry Preview with .reg files

* Add setting for making RP default app for .reg files

* Run spellcheck

* Run spellcheck again

* Fix build

---------

Co-authored-by: Stefan Markovic <stefan@janeasystems.com>

installer/PowerToysSetupCustomActions/CustomAction.cpp

@@ -123,6 +123,8 @@ UINT __stdcall UnApplyModulesRegistryChangeSetsCA(MSIHANDLE hInstall)
         changeSet.unApply();
     }
 
+    SHChangeNotify(SHCNE_ASSOCCHANGED, SHCNF_IDLIST, NULL, NULL);
+
     ExitOnFailure(hr, "Failed to extract msix");
 
 LExit:

installer/PowerToysSetupCustomActions/stdafx.h

@@ -8,6 +8,7 @@
 #include <strsafe.h>
 #include <msiquery.h>
 #include <Msi.h>
+#include <shlobj_core.h>
 
 // WiX Header Files:
 #include <wcautil.h>