This issue is about creating a /docs/Getting-started.md file with the most important information needed to contribute to the performance plugin. That documentation should follow a similar structure like Gutenberg's https://github.com/WordPress/gutenberg/blob/trunk/docs/contributors/code/getting-started-with-code-contribution.md, e.g.:

• explain how to clone the repository
• which local tools are required (Node.js, Docker)
• any commands that need to be run (e.g. linting, tests)
• high-level code requirements (e.g. follow WordPress coding standards and WordPress core coding patterns in general)

We should also include there with which WordPress and PHP versions the code should be compatible, which ties into a greater product question: Which WordPress and PHP version should we require and how far back do we support?

^ That is probably the main question to answer here before we can get started with the documentation.

In addition to the above file, which is the main part of this issue, we should also add the regular CONTRIBUTING.md file. That one can be really short and mostly link to the above documentation file. At a high level, we can look at Gutenberg's https://github.com/WordPress/gutenberg/blob/trunk/docs/contributors/code/README.md and https://github.com/WordPress/gutenberg/blob/trunk/CONTRIBUTING.md for inspiration what to include here.

The main part of this issue will be coming up with the above documentation in a PR and reviewing it.