Prebuild Codespaces workspace

[rarkins]

Describe the proposed change(s).

https://docs.github.com/en/codespaces/prebuilding-your-codespaces/about-github-codespaces-prebuilds

[HonkingGoose]

Remember to set up spending limits first, to prevent excessive bills for the Renovate organization. 😉 Here's how:

• GitHub docs, managing the spending limit for GitHub Codespaces
• GitHub docs, managing the cost of GitHub Codespaces in your organization