Add pw_string to bazel build.

Change-Id: I0aa7741959b741de082d44afe87786754b572951
diff --git a/pw_status/BUILD b/pw_status/BUILD
index 24f3b2e..31fa5de 100644
--- a/pw_status/BUILD
+++ b/pw_status/BUILD
@@ -19,7 +19,10 @@
 cc_library(
     name = "pw_status",
     srcs = ["status.cc"],
-    hdrs = ["public/pw_status/status.h"],
+    hdrs = [
+        "public/pw_status/status.h",
+        "public/pw_status/status_with_size.h",
+    ],
     copts = pw_default_copts(),
     linkopts = pw_default_linkopts(),
 )