Replace most occurrences of os.Exit(0) in the backend and sync packages with a custom backend.Exit function that can allow "soft exit" in GUI/TUI environments to avoid killing the entire process; currently all major errors still result in killing the entire process

src/backend/configParser.go

@@ -35,7 +35,7 @@ func ParseConfig(readKeys []string, missingValueError string) []string {
 			case "":
 				fmt.Println(AnsiError + "Failed to find value for key \"" + key + "\" in section \"[LIBMUTTON]\" in libmutton.ini" + AnsiReset)
 			case "0":
-				os.Exit(0)
+				Exit(0)
 			default:
 				fmt.Println(AnsiError + missingValueError + AnsiReset)
 			}