[Telemetry] Add script to snapshot page's HTML

PRESUBMIT.py

Index: PRESUBMIT.py
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index dddab1a5a0ad981896cd4740882d101a01428401..c43dff6dfa07260363581cbc60c13e849335649e 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -31,6 +31,7 @@ _EXCLUDED_PATHS = (
     r'^experimental[\\/]trace_on_tap[\\/]third_party[\\/].*',
     r'^perf_insights[\\/]test_data[\\/].*',
     r'^perf_insights[\\/]third_party[\\/].*',
+    r'^telemetry[\\/]third_party[\\/].*',
     r'^third_party[\\/].*',
     r'^tracing[\\/]\.allow-devtools-save$',
     r'^tracing[\\/]bower\.json$',