meta: add pre-upload config

In the interest of code health, we want to
run checkstyle for all of our CLs. Add checkstyle
to the pre-upload config for our project, so that
this happens automatically.

While there: also require every CL in our project
to have a BUG line.

Bug: 28291425
Test: manual

Manual test:
1. Tried "repo upload" when this commit message had
   "BUG=" and "TEST=" instead of "Bug:", and "Test:".
   Observed that the pre-upload check flagged both
   errors.
2. Tried "repo upload" with another CL, which added
   a public method, but no Javadoc for that method.
   Observed that the pre-upload check reported
   style violations.
3. Tried "repo upload" with the CL from #2 fixed,
   so that the CL was stylistically acceptable.
   Observed that the pre-upload check reported no
   problems.

Change-Id: I0be91aec4c01076eb57cad90f93f39f61833ef07
diff --git a/PREUPLOAD.cfg b/PREUPLOAD.cfg
new file mode 100644
index 0000000..d2f7a92
--- /dev/null
+++ b/PREUPLOAD.cfg
@@ -0,0 +1,7 @@
+[Hook Scripts]
+checkstyle_hook = ../../../../development/tools/checkstyle/checkstyle.py --sha ${PREUPLOAD_COMMIT}
+
+[Builtin Hooks]
+commit_msg_bug_field = true
+commit_msg_changeid_field = true
+commit_msg_test_field = true