chore: update common templates (#1001)

Author: yoshi-automation

.github/PULL_REQUEST_TEMPLATE.md

@@ -1 +1,7 @@
-Fixes #<issue_number_goes_here> (it's a good idea to open an issue first for context and/or discussion)
+Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:
+- [ ] Make sure to open an issue as a [bug/issue](https://github.com/googleapis/google-http-java-client/issues/new/choose) before writing your code!  That way we can discuss the change, evaluate designs, and agree on the general idea
+- [ ] Ensure the tests and linter pass
+- [ ] Code coverage does not decrease (if any source code was changed)
+- [ ] Appropriate docs were updated (if necessary)
+
+Fixes #<issue_number_goes_here> ☕️

.github/trusted-contribution.yml

@@ -0,0 +1,2 @@
+trustedContributors:
+- renovate-bot

synth.metadata

@@ -1,5 +1,5 @@
 {
-  "updateTime": "2020-03-02T22:34:09.877226Z",
+  "updateTime": "2020-03-13T21:34:17.479284Z",
   "sources": [
     {
       "template": {