perf buildid-cache: Document for Node.js USDT

Add a tip for Node.js USDT(User-Level Statically Defined Tracing) probes
in tips.txt

Signed-off-by: Hansuk Hong <flavono123@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20171123160546.9722-1-flavono123@gmail.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>