STORY: Update template - Pull Requests

[brmur]

As an engineer on this team, I want a pull request template improved in the following ways:

• cleaner to read
• easier to follow
• elicits all required information to action.
• reflects current process (documented here).

So that:

• requests all the information required to be initially understood & triaged internally in 1 minute
• it can be completed in less than 5 minutes, assuming user has all the required info, without the need for back-and-forth questions

And I know this is done when:

• a PR against PULL_REQUEST_TEMPLATE.md is raised, reviewed, and merged
• process documentation is updated where appropriate

[ford-at-aws]

Close relative of https://github.com/awsdocs/aws-doc-sdk-examples/issues/3295. Not duplicate.

@meyertst-aws will do the following:

1. ask team for anecdotes about issue template problems
2. collect data on current issue (e.g. created by whom?)
3. spent 1 hr coming up with a simplified version of each of the existing templates as an exercise (will share w/ team via Quip)
4. add the findings from these items to a shared Quip doc