docs(example): simple example showing conditional options (#75)

* docs(example): simple example showing conditional options

* refactor: conditional to use WithHideFunc groups

this allows the form to be navigated and the user to choose another
option by going back.

---------

Co-authored-by: Maas Lalani <maas@lalani.dev>

examples/conditional/main.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/charmbracelet/huh"
+)
+
+type consumable int
+
+const (
+	fruits consumable = iota
+	vegetables
+	drinks
+)
+
+func (c consumable) String() string {
+	return [...]string{"fruit", "vegetable", "drink"}[c]
+}
+
+func main() {
+
+	var category consumable
+	type opts []huh.Option[string]
+
+	var choice string
+
+	// Then ask for a specific food item based on the previous answer.
+	err :=
+		huh.NewForm(
+			huh.NewGroup(
+				huh.NewSelect[consumable]().
+					Title("What are you in the mood for?").
+					Value(&category).
+					Options(
+						huh.NewOption("Some fruit", fruits),
+						huh.NewOption("A vegetable", vegetables),
+						huh.NewOption("A drink", drinks),
+					),
+			),
+
+			huh.NewGroup(
+				huh.NewSelect[string]().
+					Title("Okay, what kind of fruit are you in the mood for?").
+					Options(
+						huh.NewOption("Tangerine", "tangerine"),
+						huh.NewOption("Canteloupe", "canteloupe"),
+						huh.NewOption("Pomelo", "pomelo"),
+						huh.NewOption("Grapefruit", "grapefruit"),
+					).
+					Value(&choice),
+			).WithHideFunc(func() bool { return category != fruits }),
+
+			huh.NewGroup(
+				huh.NewSelect[string]().
+					Title("Okay, what kind of vegetable are you in the mood for?").
+					Options(
+						huh.NewOption("Carrot", "carrot"),
+						huh.NewOption("Jicama", "jicama"),
+						huh.NewOption("Kohlrabi", "kohlrabi"),
+						huh.NewOption("Fennel", "fennel"),
+						huh.NewOption("Ginger", "ginger"),
+					).
+					Value(&choice),
+			).WithHideFunc(func() bool { return category != vegetables }),
+
+			huh.NewGroup(
+				huh.NewSelect[string]().
+					Title(fmt.Sprintf("Okay, what kind of %s are you in the mood for?", category)).
+					Options(
+						huh.NewOption("Coffee", "coffee"),
+						huh.NewOption("Tea", "tea"),
+						huh.NewOption("Bubble Tea", "bubble tea"),
+						huh.NewOption("Agua Fresca", "agua-fresca"),
+					).
+					Value(&choice),
+			).WithHideFunc(func() bool { return category != drinks }),
+		).Run()
+
+	if err != nil {
+		fmt.Println("Trouble in food paradise:", err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("One %s coming right up!\n", choice)
+}