chore: Update PR template to ensure issue is linked and clarify when examples/docs should be added

[bryantbiggs]

What does this PR do?

• Add a templated line for Resolves #<xxx> to help guide users to autolink issues to PRs
• Add clarifying note on using existing examples to demonstrate addon usage and add a docs page when adding an addon

Motivation

• Updating project general practices

More

• Yes, I have tested the PR using my local account setup (Provide any test evidence report under Additional Notes)
• Yes, I have added a new example under examples to support my PR
• Yes, I have created another PR for add-ons under add-ons repo (if applicable)
• Yes, I have updated the docs for this feature
• Yes, I ran pre-commit run -a with this PR

Note: Not all the PRs required examples and docs except a new pattern or add-on added.

For Moderators

• E2E Test successfully complete before merge?

Additional Notes

[csantanapr]

/lgtm

[bryantbiggs]

we're not that fancy (*yet) 😅