docs: update pull request template for improved clarity and formatting

[SalemBajjali]

Resolves: #199

Updates the PR template to better reflect the current development workflow and generalize it. This approach was discussed with @brendanreardon during GKS-ThinkTank.

Before modifying the template, I reviewed the existing development workflow and organized the checklist to reflect the following steps:

• Compile schema
• Write/update tests
• Document schema changes
• Register new .rst files (if created)
• Build docs locally

[brendanreardon]

I LOVE this! Thank you so much, @SalemBajjali!

Do you think that it makes sense to wait for all products to approve the PR before simultaneously merging them? I can imagine benefits both ways. It could take a while to get each product to approve the PR, and not waiting could result in subsequent required PRs to make sure that all of the products are sync'd. To that end, I'm going to assign myself and @korikuzma as reviewers. If Kori is happy with the template then maybe she can make the executive decision to add it as is to all of the other repos.

[korikuzma]

I think this is a good start! I have some minor suggestions

[korikuzma]

Suggested change

	## Summary of the Pull Request.
	## Summary of the Pull Request

[korikuzma]

Suggested change

	## Pull Request checklist:
	## Pull Request checklist

[korikuzma]

Suggested change

	### If the schema or examples were contributed to:
	### Required if the schema or examples were contributed to

[korikuzma]

I wonder if we should phrase as a confirmation rather than question?

Suggested change

	- [ ] Does the title of this Pull Request reference the corresponding Issue?
	- [ ] Is the branch validating against pre-commit hooks? Run `pre-commit run --all-files` from the root directory.
	- [ ] Is the branch passing tests? Run `pytest tests/` from the root directory.
	- [ ] The title of this Pull Request accurately reflects the scope and content of the linked Issue.
	- [ ] The branch passes all pre-commit hooks (Run `pre-commit run --all-files` from the root directory).
	- [ ] The branch passes all tests (Run `pytest tests` from the root directory).

[korikuzma]

Same as above: I wonder if we should phrase as a confirmation rather than question?

Suggested change

	- [ ] Were the schema `def/` and `json/` files recompiled and committed? Run `cd schema; make all` from the root directory.
	- [ ] Have tests been created or updated?
	- [ ] Have schema changes been documented (update existing files or create new ones in `docs/source/`)?
	- [ ] If new `.rst` files were created, have they been registered in the documentation structure?
	- [ ] Has documentation been regenerated and committed? Run `cd docs; make clean watch &` from the root directory to compile documentation.
	- [ ] The schema `def/` and `json/` files have been recompiled and committed (Run `cd schema; make all` from the root directory).
	- [ ] Tests have been created or updated.
	- [ ] Schema changes have been documented (existing files updated or new files created in `docs/source/`).
	- [ ] Any new `.rst` files have been registered in the documentation structure.
	- [ ] Documentation has been regenerated and committed (Run `cd docs; make clean watch &` from the root directory).