add an example using UI & states to create a game menu (#2960)

adds an example using UI for something more related to a game than the current UI examples.

Example with a game menu:
* new game - will display settings for 5 seconds before returning to menu
* preferences - can modify the settings, with two sub menus
* quit - will quit the game


I wanted a more complex UI example before starting the UI rewrite to have ground for comparison

Co-authored-by: François <8672791+mockersf@users.noreply.github.com>

CREDITS.md

@@ -16,3 +16,7 @@
 
 * Generic RPG Pack (CC0 license) by [Bakudas](https://twitter.com/bakudas) and [Gabe Fern](https://twitter.com/_Gabrielfer)
 * Environment maps (`.hdr` files) from [HDRIHaven](https://hdrihaven.com) (CC0 license)
+* Alien from [Kenney's Space Kit](https://www.kenney.nl/assets/space-kit) (CC0 1.0 Universal)
+* Cake from [Kenney's Food Kit](https://www.kenney.nl/assets/food-kit) (CC0 1.0 Universal)
+* Ground tile from [Kenney's Tower Defense Kit](https://www.kenney.nl/assets/tower-defense-kit) (CC0 1.0 Universal)
+* Game icons from [Kenney's Game Icons](https://www.kenney.nl/assets/game-icons) (CC0 1.0 Universal)

Cargo.toml

@@ -359,6 +359,10 @@ path = "examples/game/alien_cake_addict.rs"
 name = "breakout"
 path = "examples/game/breakout.rs"
 
+[[example]]
+name = "game_menu"
+path = "examples/game/game_menu.rs"
+
 # Input
 [[example]]
 name = "char_input_events"

examples/README.md

@@ -182,6 +182,7 @@ Example | File | Description
 --- | --- | ---
 `alien_cake_addict` | [`game/alien_cake_addict.rs`](./game/alien_cake_addict.rs) | Eat the cakes. Eat them all. An example 3D game
 `breakout` | [`game/breakout.rs`](./game/breakout.rs) | An implementation of the classic game "Breakout"
+`game_menu` | [`game/game_menu.rs`](./game/game_menu.rs) | A simple game menu
 
 ## Input