v2 lightning docs: refresh CLI pages

[aleksa-krolls]

Request

In the new v2 docs section Build Workflows - For Developers, we want to add/refresh the following docs pages:

• Intro to the OpenFn CLI (see docs/build-for-developers/cli-intro.md)
• CLI Installation & Usage (see docs/build-for-developers/cli-usage.md)
• CLI Tutorial (see docs/build-for-developers/cli-tutorial.md)
• Testing workflows with the CLI (NEW page to add? Or does this content already exist somewhere?)

I recommend starting with 1 page --> get feedback from me & Nick on the page structure and look --> and then proceed with the rest.

If you have any comments or ideas for new pages, please leave notes in the docs Information Architecture sheet.

For review

Create a new branch off of main and draft a PR with these changes for review. Assign to me when ready for review.

Resources

Before you start work, please review Nick's thoughts on how to write docs.

See the Docs Style Guide for other guidance when writing in markdown.