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

README.md

@@ -18,6 +18,9 @@ go install git.warky.dev/wdevs/pgtidy/cmd/pgtidy@latest
 
 Or download a pre-built binary from [Releases](https://git.warky.dev/wdevs/pgtidy/releases).
 
+**Windows** — run `pgtidy-setup-windows-amd64.exe` from the release. It installs to
+`%ProgramFiles%\PgTidy` and adds it to the system `PATH`. Update later with `pgtidy update`.
+
 ---
 
 ## CLI
@@ -27,6 +30,7 @@ pgtidy fmt    [flags] [files...]   Format SQL/PL-pgSQL (stdin if no files)
 pgtidy lint   [flags] [files...]   Lint SQL
 pgtidy config                      Print effective configuration
 pgtidy lsp                         Start LSP server (stdio)
+pgtidy update [--check] [-y]       Check for a newer release (installs it on Windows)
 pgtidy version
 ```