MangoHud: add mangoapp sub-package

`mangoapp` is required if you wish to use MangoHud within a `gamescope`
session. From the MangoHud README...

> To enable mangohud with gamescope you need to install mangoapp.
> `gamescope --mangoapp %command%`
>
> Using normal mangohud with gamescope is not supported.

closes #53633

srcpkgs/MangoHud-mangoapp

@@ -0,0 +1 @@
+MangoHud

srcpkgs/MangoHud/template

@@ -4,10 +4,10 @@ version=0.8.0
 revision=1
 build_style=meson
 configure_args="-Dwith_xnvctrl=disabled
- -Dwith_nvml=disabled -Duse_system_spdlog=enabled"
+ -Dwith_nvml=disabled -Duse_system_spdlog=enabled -Dmangoapp=true"
 hostmakedepends="Vulkan-Headers python3-Mako glslang pkg-config"
 makedepends="libglvnd-devel dbus-devel vulkan-loader spdlog json-c++
- wayland-devel libxkbcommon-devel"
+ wayland-devel libxkbcommon-devel glfw-devel glew-devel"
 short_desc="Vulkan and OpenGL overlay for monitoring FPS, temperatures and more"
 maintainer="Orphaned <orphan@voidlinux.org>"
 license="MIT"
@@ -24,3 +24,12 @@ fi
 post_install() {
 	vlicense LICENSE
 }
+
+MangoHud-mangoapp_package() {
+	short_desc="Transparent background application with a built in mangohud"
+	depends="${sourcepkg}>=${version}_${revision}"
+	pkg_install() {
+		vmove usr/bin/mangoapp
+		vmove usr/share/man/man1/mangoapp.1
+	}
+}