Add entt (#298)

* Add entt

* Update xmake.lua

* Update xmake.lua

* Update xmake.lua

* Update xmake.lua

packages/e/entt/xmake.lua

@@ -0,0 +1,24 @@
+package("entt")
+
+    set_homepage("https://github.com/skypjack/entt")
+    set_description("Gaming meets modern C++ - a fast and reliable entity component system (ECS) and much more.")
+
+    set_urls("https://github.com/skypjack/entt/archive/$(version).tar.gz",
+             "https://github.com/skypjack/entt.git")
+
+    add_versions("v3.6.0", "94b7dc874acd0961cfc28cf6b0342eeb0b7c58250ddde8bdc6c101e84b74c190")
+    add_deps("cmake")
+
+    on_install(function (package)
+        local configs = {}
+        import("package.tools.cmake").install(package, configs)
+    end)
+
+    on_test(function (package)
+        assert(package:check_cxxsnippets({test = [[
+            #include <entt/entt.hpp>
+            void test() {
+                entt::registry r;
+            }
+        ]]}, {configs = {languages = "c++17"}}))
+    end)