Update docs

Author: dearchap

docs/migrate-v2-to-v3.md

@@ -123,7 +123,7 @@ in addition to other specific args. This allows handler functions to utilize con
 blocking/time-specific operations and so on
 
 * OLD: `type BeforeFunc func(*Context) error`
-* NEW: `type BeforeFunc func(context.Context, *cli.Command) error`
+* NEW: `type BeforeFunc func(context.Context, *cli.Command) (context.Context, error)`
 
 * OLD: `type AfterFunc func(*Context) error`
 * NEW: `type AfterFunc func(context.Context, *cli.Command) error`

docs/v3/examples/full-api-example.md

@@ -153,9 +153,9 @@ func main() {
 		ShellComplete: func(ctx context.Context, cmd *cli.Command) {
 			fmt.Fprintf(cmd.Root().Writer, "lipstick\nkiss\nme\nlipstick\nringo\n")
 		},
-		Before: func(ctx context.Context, cmd *cli.Command) error {
+		Before: func(ctx context.Context, cmd *cli.Command) (context.Context, error) {
 			fmt.Fprintf(cmd.Root().Writer, "HEEEERE GOES\n")
-			return nil
+			return nil, nil
 		},
 		After: func(ctx context.Context, cmd *cli.Command) error {
 			fmt.Fprintf(cmd.Root().Writer, "Phew!\n")