[dv/alert_handler] Add dv plan

Add alert_handler dv plan draft
Add alert_handler testplan
Signed-off-by: Cindy Chen <chencindy@google.com>
diff --git a/util/build_docs.py b/util/build_docs.py
index f928212..d6fb3b0 100755
--- a/util/build_docs.py
+++ b/util/build_docs.py
@@ -72,6 +72,7 @@
     # Pre-generate testplan fragments from these files.
     "testplan_definitions": [
         "hw/ip/aes/data/aes_testplan.hjson",
+        "hw/ip/alert_handler/data/alert_handler_testplan.hjson",
         "hw/ip/gpio/data/gpio_testplan.hjson",
         "hw/ip/hmac/data/hmac_testplan.hjson",
         "hw/ip/i2c/data/i2c_testplan.hjson",