feat(windows): rewrite NSIS installer, add pgtidy update command

cmd/pgtidy/main.go

@@ -28,6 +28,8 @@ func run(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
 		return cmdLsp(args[1:], stdin, stdout, stderr)
 	case "config":
 		return cmdConfig(args[1:], stdin, stdout, stderr)
+	case "update":
+		return cmdUpdate(args[1:], stdin, stdout, stderr)
 	case "version", "--version", "-v":
 		_, _ = fmt.Fprintf(stdout, "pgtidy %s\n", version)
 		return 0
@@ -49,6 +51,7 @@ Usage:
   pgtidy lint   [flags] [files...]  Lint SQL (stdin if no files)
   pgtidy config                     Print effective configuration
   pgtidy lsp                        Start LSP server (stdio, for editors)
+  pgtidy update [--check] [-y]      Check for a newer release (installs on Windows)
   pgtidy version                    Print version
   pgtidy help                       Show this help