build sample with cmake on Linux

tools/playground/CMakeLists.txt

@@ -0,0 +1,8 @@
+add_executable(playgound
+    camera.cpp font.cpp main.cpp ras_test.cpp splines.cpp tl_tests.cpp
+)
+
+target_link_libraries(playgound
+    PUBLIC
+        librw librw_skeleton
+)