signal: show Windows popup window on crash (#410)

## Link to GitHub Issue, if one exists
#345 

## Description of change
Show a MessageBox when signal detects a crash.

## Testing
Tested full screen and windowed games.

src/spice2x/launcher/signal.cpp

@@ -1,5 +1,6 @@
 #include "signal.h"
 
+#include <future>
 #include <exception>
 
 #include <windows.h>
@@ -174,6 +175,18 @@ static LONG WINAPI TopLevelExceptionFilter(struct _EXCEPTION_POINTERS *Exception
             log_warning("signal", "minidump creation function not available, skipping");
         }
 
+        // reduce sleep time since we will wait for the user to acknowledge the popup
+        LOG_FATAL_SLEEP = 1;
+
+        // in 30 seconds, shut down (in case user can't dismiss popup)
+        const auto f = std::async(std::launch::async, [] {
+            std::this_thread::sleep_for(std::chrono::seconds(30));
+            log_fatal("signal", "end");
+        });
+
+        // this will stall all UI threads for this process
+        deferredlogs::show_popup_for_crash();
+
         log_fatal("signal", "end");
     }