Add Truth java8 extensions (truth8) to third_party.

RELNOTES: None.

Change-Id: I9f9295df15edf1f701e9003bca4021f78540c1eb
diff --git a/third_party/BUILD b/third_party/BUILD
index 2005db6..6dd8bb7 100644
--- a/third_party/BUILD
+++ b/third_party/BUILD
@@ -525,6 +525,11 @@
 )
 
 java_import(
+    name = "truth8",
+    jars = ["truth8/truth-java8-extension-0.36.jar"],
+)
+
+java_import(
     name = "xz",
     jars = ["xz/xz-1.5.jar"],
 )