add EnTT example (#78)

examples/entt/CMakeLists.txt

@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+# ---- Dependencies ----
+
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME EnTT
+  VERSION 3.1.1
+  GITHUB_REPOSITORY skypjack/entt
+  # EnTT's CMakeLists screws with configuration options
+  DOWNLOAD_ONLY True
+)
+
+if (EnTT_ADDED)
+  add_library(EnTT INTERFACE)
+  target_include_directories(EnTT INTERFACE ${EnTT_SOURCE_DIR}/src)
+endif()
+
+# ---- Executable ----
+
+add_executable(CPMEnTTExample "main.cpp")
+set_target_properties(CPMEnTTExample PROPERTIES CXX_STANDARD 17)        
+target_link_libraries(CPMEnTTExample EnTT)