feat(glfw): adapter and 1 MS/s streaming demo

CMakeLists.txt

@@ -43,3 +43,14 @@ if(PLOT_BUILD_TESTS)
   enable_testing()
   add_subdirectory(tests)
 endif()
+
+# Adapters own the surface and translate their host's events; examples link the
+# adapter they demo. Both are opt-in, so the core library and its tests still
+# build on a bare toolchain.
+if(PLOT_BUILD_GLFW)
+  add_subdirectory(adapters/glfw)
+endif()
+
+if(PLOT_BUILD_EXAMPLES)
+  add_subdirectory(examples)
+endif()