meson: Add missing examples directory

This will make it more visible what is missing in meson.

tests/examples/meson.build

@@ -1,6 +1,19 @@
 # FIXME - Add other missing examples!
+#subdir('audiomixmatrix')
+#subdir('avsamplesink')
+#subdir('camerabin2')
+#subdir('codecparsers')
 subdir('compositor')
+#subdir('directfb')
+#subdir('gl')
+#subdir('gtk')
+#subdir('ipcpipeline')
 subdir('mpegts')
+#subdir('mxf')
+#subdir('opencv')
+#subdir('qt')
+#subdir('uvch264')
+#subdir('waylandsink')
 
 if build_gstgl and gstgl_dep.found()
   executable('playout',