Reminders in PR Template

[danielduan]

Issue:

Contributors, new and old, sometimes forget to add tests, update storyshots, include examples in the kitchen-sink apps, etc. I'm definitely guilty. If we have a list of reminders at the bottom, it might help cut down on our time wasted asking for test and examples to be written.

Definitely open to suggestions here!

[codecov]

Codecov Report

Merging #1683 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1683   +/-   ##
=======================================
  Coverage   20.87%   20.87%           
=======================================
  Files         251      251           
  Lines        5629     5629           
  Branches      693      693           
=======================================
  Hits         1175     1175           
  Misses       3924     3924           
  Partials      530      530

Impacted Files	Coverage Δ
...es__/update-addon-info/update-addon-info.output.js	0% <0%> (ø)	⬆️
...rc/modules/ui/components/left_panel/text_filter.js	34.24% <0%> (ø)	⬆️
lib/ui/src/modules/ui/libs/filters.js	53.33% <0%> (ø)	⬆️
addons/info/src/components/PropVal.js	43.15% <0%> (ø)	⬆️
lib/ui/src/modules/ui/containers/down_panel.js	23.52% <0%> (ø)	⬆️
addons/knobs/src/components/PropField.js	10.86% <0%> (ø)	⬆️
app/react-native/src/preview/story_kind.js	0% <0%> (ø)	⬆️
lib/ui/src/modules/ui/libs/hierarchy.js	45.45% <0%> (ø)	⬆️
addons/info/src/components/PropTable.js	20.16% <0%> (ø)	⬆️
lib/ui/src/modules/ui/containers/layout.js	12.5% <0%> (ø)	⬆️
... and 16 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2f5000d...3ac6c76. Read the comment docs.