chore: add pull request and issue templates

Description

Added in some templates for issues and a checklist for pull-requests, inspired by the CDK.

Issue templates

These templates will be used for users who create Issues for the repo. Users will be presented with options based on whether they are filing a feature-request, bug, or doc.

Pull request template:

This template will be applied whenever a pull request is

Note: one difference between the current message is that the licensing text has been updated to reflect the license we use in the repo

Templates are pretty self-explanatory in terms of the details we will request.

Open

We may need to make some updates to CONTRIBUTING guide but wanted to settle on content first
- i.e. do we want to follow conventional commits - i just kind of threw that in the PR checklist
How is the current PR boilerplate content generated? I think it's default but want to confirm we haven't configured it anywhere

The questions/directives are somewhat opinionated, but your opinion matters the most. drop a comment 👇 and I'll work it in

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

aws / aws-step-functions-data-science-sdk-python