chore: update PR template (googleapis#49)

This PR was generated using Autosynth. 🌈


<details><summary>Log from Synthtool</summary>

```
2020-03-14 02:17:05,245 synthtool > Executing /tmpfs/src/git/autosynth/working_repo/synth.py.
.github/ISSUE_TEMPLATE/bug_report.md
.github/ISSUE_TEMPLATE/feature_request.md
.github/ISSUE_TEMPLATE/support_request.md
.github/PULL_REQUEST_TEMPLATE.md
.github/release-please.yml
.github/trusted-contribution.yml
.kokoro/build.bat
.kokoro/build.sh
.kokoro/coerce_logs.sh
.kokoro/common.cfg
.kokoro/continuous/common.cfg
.kokoro/continuous/dependencies.cfg
.kokoro/continuous/integration.cfg
.kokoro/continuous/java11.cfg
.kokoro/continuous/java7.cfg
.kokoro/continuous/java8-osx.cfg
.kokoro/continuous/java8-win.cfg
.kokoro/continuous/java8.cfg
.kokoro/continuous/lint.cfg
.kokoro/continuous/propose_release.cfg
.kokoro/continuous/samples.cfg
.kokoro/dependencies.sh
.kokoro/linkage-monitor.sh
.kokoro/nightly/common.cfg
.kokoro/nightly/dependencies.cfg
.kokoro/nightly/integration.cfg
.kokoro/nightly/java11.cfg
.kokoro/nightly/java7.cfg
.kokoro/nightly/java8-osx.cfg
.kokoro/nightly/java8-win.cfg
.kokoro/nightly/java8.cfg
.kokoro/nightly/lint.cfg
.kokoro/nightly/samples.cfg
.kokoro/presubmit/clirr.cfg
.kokoro/presubmit/common.cfg
.kokoro/presubmit/dependencies.cfg
.kokoro/presubmit/integration.cfg
.kokoro/presubmit/java11.cfg
.kokoro/presubmit/java7.cfg
.kokoro/presubmit/java8-osx.cfg
.kokoro/presubmit/java8-win.cfg
.kokoro/presubmit/java8.cfg
.kokoro/presubmit/linkage-monitor.cfg
.kokoro/presubmit/lint.cfg
.kokoro/presubmit/samples.cfg
.kokoro/release/bump_snapshot.cfg
.kokoro/release/common.cfg
.kokoro/release/common.sh
.kokoro/release/drop.cfg
.kokoro/release/drop.sh
.kokoro/release/promote.cfg
.kokoro/release/promote.sh
.kokoro/release/publish_javadoc.cfg
.kokoro/release/publish_javadoc.sh
.kokoro/release/snapshot.cfg
.kokoro/release/snapshot.sh
.kokoro/release/stage.cfg
.kokoro/release/stage.sh
.kokoro/trampoline.sh
CODE_OF_CONDUCT.md
CONTRIBUTING.md
LICENSE
README.md
codecov.yaml
java.header
license-checks.xml
renovate.json
2020-03-14 02:17:05,439 synthtool > Wrote metadata to synth.metadata.

```
</details>

.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/java-storage-nio/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> ☕️

synth.metadata

@@ -1,5 +1,5 @@
 {
-  "updateTime": "2020-02-27T18:25:22.358985Z",
+  "updateTime": "2020-03-14T09:17:05.438962Z",
   "sources": [
     {
       "template": {