add to our yaml style best practice guide (#6662)

Closes #1686
## What are you changing in this pull request and why?

* added that a YAML list is accepted as a string.
* Not adding a new page because winnie did this amazing best practice
guide after this issue was filed.

## Checklist
- [ ] I have reviewed the [Content style
guide](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/content-style-guide.md)
so my content adheres to these guidelines.
- [ ] The topic I'm writing about is for specific dbt version(s) and I
have versioned it according to the [version a whole
page](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#adding-a-new-version)
and/or [version a block of
content](https://github.com/dbt-labs/docs.getdbt.com/blob/current/contributing/single-sourcing-content.md#versioning-blocks-of-content)
guidelines.
- [ ] I have added checklist item(s) to this list for anything anything
that needs to happen before this PR is merged, such as "needs technical
review" or "change base branch."
- [ ] The content in this PR requires a dbt release note, so I added one
to the [release notes
page](https://docs.getdbt.com/docs/dbt-versions/dbt-cloud-release-notes).
<!--
PRE-RELEASE VERSION OF dbt (if so, uncomment):
- [ ] Add a note to the prerelease version [Migration
Guide](https://github.com/dbt-labs/docs.getdbt.com/tree/current/website/docs/docs/dbt-versions/core-upgrade)
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<!-- 
ADDING OR REMOVING PAGES (if so, uncomment):
- [ ] Add/remove page in `website/sidebars.js`
- [ ] Provide a unique filename for new pages
- [ ] Add an entry for deleted pages in `website/vercel.json`
- [ ] Run link testing locally with `npm run build` to update the links
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<!-- vercel-deployment-preview -->
---
🚀 Deployment available! Here are the direct links to the updated files:


-
https://docs-getdbt-com-git-runleonarun-patch-16-dbt-labs.vercel.app/best-practices/how-we-style/5-how-we-style-our-yaml

<!-- end-vercel-deployment-preview -->

---------

Co-authored-by: Matt Shaver <[email protected]>

website/docs/best-practices/how-we-style/5-how-we-style-our-yaml.md

@@ -7,6 +7,7 @@ id: 5-how-we-style-our-yaml
 
 - 2️⃣ Indents should be two spaces
 - ➡️ List items should be indented
+- 🔠 List items with a single entry can be a string. For example, `'select': 'other_user'`, but it's best practice to provide the argument as an explicit list. For example, `'select': ['other_user']`
 - 🆕 Use a new line to separate list items that are dictionaries where appropriate
 - 📏 Lines of YAML should be no longer than 80 characters.
 - 🛠️ Use the [dbt JSON schema](https://github.com/dbt-labs/dbt-jsonschema) with any compatible IDE and a YAML formatter (we recommend [Prettier](https://prettier.io/)) to validate your YAML files and format them automatically.