docs: use spaces in readme code blocks

Author: rlibaert

README.md

@@ -14,55 +14,55 @@ Package `flag/cli` provides a very simple interface for building command-lines a
 
 ```go
 func main() {
-	cmd := &cli.Command{
-		Name:      os.Args[0],
-		Usage:     "A sample application",
-		UsageArgs: "[arguments]",
-		Flags: func(fs *flag.FlagSet) {
-			fs.Bool("verbose", false, "enable verbose output")
-		},
-		RunContext: func(parent context.Context, run func(ctx context.Context) error) error {
-			ctx, cancel := signal.NotifyContext(parent, os.Interrupt)
-			defer cancel()
-			return run(ctx)
-		},
-		Subcommands: []*cli.Command{
-			{
-				Name:  "serve",
-				Usage: "Start the server",
-				Flags: func(fs *flag.FlagSet) {
-					fs.String("config", "config.yaml", "configuration file (env $MYAPP_CONFIG)")
-					fs.Int("port", 8080, "port to listen on")
-				},
-				FlagsEnvMap: map[string]string{
-					"config": "MYAPP_CONFIG",
-				},
-				FlagsRequired: []string{"config"},
-				Func: func(ctx context.Context, args []string) error {
-					fmt.Printf("starting server on port %d with config %s (verbose: %v)\n",
-						cli.Get(ctx, "port").(int),
-						cli.Get(ctx, "config").(string),
-						cli.Get(ctx, "verbose").(bool),
-					)
-					return nil
-				},
-			},
-			{
-				Name:  "version",
-				Usage: "Show version information",
-				Func: func(ctx context.Context, args []string) error {
-					fmt.Println("vX.Y.Z")
-					return nil
-				},
-			},
-		},
-	}
-
-	err := cmd.Run(context.Background(), os.Args[1:])
-	if err != nil && err != flag.ErrHelp {
-		fmt.Fprintf(os.Stderr, "error: %v\n", err)
-		os.Exit(2)
-	}
+    cmd := &cli.Command{
+        Name:      os.Args[0],
+        Usage:     "A sample application",
+        UsageArgs: "[arguments]",
+        Flags: func(fs *flag.FlagSet) {
+            fs.Bool("verbose", false, "enable verbose output")
+        },
+        RunContext: func(parent context.Context, run func(ctx context.Context) error) error {
+            ctx, cancel := signal.NotifyContext(parent, os.Interrupt)
+            defer cancel()
+            return run(ctx)
+        },
+        Subcommands: []*cli.Command{
+            {
+                Name:  "serve",
+                Usage: "Start the server",
+                Flags: func(fs *flag.FlagSet) {
+                    fs.String("config", "config.yaml", "configuration file (env $MYAPP_CONFIG)")
+                    fs.Int("port", 8080, "port to listen on")
+                },
+                FlagsEnvMap: map[string]string{
+                    "config": "MYAPP_CONFIG",
+                },
+                FlagsRequired: []string{"config"},
+                Func: func(ctx context.Context, args []string) error {
+                    fmt.Printf("starting server on port %d with config %s (verbose: %v)\n",
+                        cli.Get(ctx, "port").(int),
+                        cli.Get(ctx, "config").(string),
+                        cli.Get(ctx, "verbose").(bool),
+                    )
+                    return nil
+                },
+            },
+            {
+                Name:  "version",
+                Usage: "Show version information",
+                Func: func(ctx context.Context, args []string) error {
+                    fmt.Println("vX.Y.Z")
+                    return nil
+                },
+            },
+        },
+    }
+
+    err := cmd.Run(context.Background(), os.Args[1:])
+    if err != nil && err != flag.ErrHelp {
+        fmt.Fprintf(os.Stderr, "error: %v\n", err)
+        os.Exit(2)
+    }
 }
 ```
 ```
@@ -103,12 +103,12 @@ Package `flag/values` provides generic implementations of the standard Go `flag.
 
 ```go
 func main() {
-	flag.Var(values.Basic[int](), "count", "number of items")
-	flag.Var(values.BasicList[string](), "tag", "tags (can be specified multiple times)")
-	flag.Var(values.BasicSlice[string](","), "regions", "comma-separated list of regions")
-	flag.Var(values.Stringer(url.Parse), "endpoint", "API endpoint URL")
-	flag.Parse()
-	flag.VisitAll(func(f *flag.Flag) { fmt.Printf("%s: %v\n", f.Name, f.Value.(flag.Getter).Get()) })
+    flag.Var(values.Basic[int](), "count", "number of items")
+    flag.Var(values.BasicList[string](), "tag", "tags (can be specified multiple times)")
+    flag.Var(values.BasicSlice[string](","), "regions", "comma-separated list of regions")
+    flag.Var(values.Stringer(url.Parse), "endpoint", "API endpoint URL")
+    flag.Parse()
+    flag.VisitAll(func(f *flag.Flag) { fmt.Printf("%s: %v\n", f.Name, f.Value.(flag.Getter).Get()) })
 }
 ```
 ```
@@ -123,16 +123,16 @@ Alternatively, the `Registerer` provides an interface analogous to `flag.FlagSet
 
 ```go
 func main() {
-	var (
-		reg   = values.FlagSetRegisterer(flag.CommandLine)
-		count = reg.Int("count", 10, "number of items")
-		email = reg.MailAddr("email", &mail.Address{}, "contact email")
-		bind  = reg.IPAddrPort("bind", netip.MustParseAddrPort("0.0.0.0:8080"), "binding address")
-	)
-	flag.Parse()
-	fmt.Printf("Count: %d\n", *count)
-	fmt.Printf("Email: %v\n", *email)
-	fmt.Printf("Bind: %v\n", *bind)
+    var (
+        reg   = values.FlagSetRegisterer(flag.CommandLine)
+        count = reg.Int("count", 10, "number of items")
+        email = reg.MailAddr("email", &mail.Address{}, "contact email")
+        bind  = reg.IPAddrPort("bind", netip.MustParseAddrPort("0.0.0.0:8080"), "binding address")
+    )
+    flag.Parse()
+    fmt.Printf("Count: %d\n", *count)
+    fmt.Printf("Email: %v\n", *email)
+    fmt.Printf("Bind: %v\n", *bind)
 }
 ```
 ```