👌 Detect binary paths (#144)

This change introduces binary detection to the app. PHP Monitor does not
rely on the user's PATH because the output of a user's terminal can
cause issues, so we will scan the two common locations for the Composer
binary file. The text in the alert has been modified to accommodate the
change (you could still not have Composer installed).

phpmon/Domain/Menu/MainMenu+Startup.swift

@@ -76,6 +76,8 @@ extension MainMenu {
             Log.info("PHP Monitor has extracted the version number of Valet: \(Valet.shared.version!)")
         }
         
+        Paths.shared.detectBinaryPaths()
+        
         Valet.shared.loadConfiguration()
         Valet.shared.validateVersion()
         Valet.shared.startPreloadingSites()