feat: support for Gatsby v5

[ericapisani]

Summary

Include .nvmrc files in both demos to specify minimum node versions in order to make it easy to work with now that there are different minimum node versions for the 2 demos.

I opted to create a 2nd demo site as we will have to continue to support v4 for the time being (will be until end of 2023 as that is how long Gatsby will maintain it, though will only have maintenance changes done to it).

I've also updated the minimum version of react to 18 in e2e tests that have gatsby@next being installed. We may want to consider having more e2e tests to ensure v4 functionality is maintained, but at the moment e2e tests take a while to run and I wanted to have that discussion with the broader team.

Dependant PR: netlify/gatsby-plugin-netlify#203

Migration guide from Gatsby - https://www.gatsbyjs.com/docs/reference/release-notes/migrating-from-v4-to-v5/

Test plan

1. Visit the Deploy Preview - https://ep-gatsby-v5--ep-gatsby-v5.netlify.app

• Confirm that the SSR and DSG pages continue to work as expected

2. Visit the v4 deploy preview - https://deploy-preview-547--netlify-plugin-gatsby-demo.netlify.app/

• Confirm the links work as expected
• Visit the api/users/123 to confirm that the page doesn't crash (this confirms the updated import logic here works as expected

Relevant links (GitHub issues, Notion docs, etc.) or a picture of cute animal

Fixes https://github.com/netlify/pod-ecosystem-frameworks/issues/269 , netlify/gatsby-plugin-netlify#195

Standard checks:

• Check the Deploy Preview's Demo site for your PR's functionality
• Add docs when necessary

[netlify]

✅ Deploy Preview for ep-gatsby-v5 canceled.

Name	Link
🔨 Latest commit	da7e52f
🔍 Latest deploy log	https://app.netlify.com/sites/ep-gatsby-v5/deploys/6398916232320a0008f0b17d

[netlify]

✅ Deploy Preview for netlify-plugin-gatsby-demo canceled.

Name	Link
🔨 Latest commit	da7e52f
🔍 Latest deploy log	https://app.netlify.com/sites/netlify-plugin-gatsby-demo/deploys/639891624f30ac0008837dfc

[ericapisani]

Based on conversations with our build team, this PR is blocked at the moment pending full support for node 18 in our build systems (see this slack thread) and some framework detection enhancements.

[nickytonline]

Ran through the two deploy previews and everything is behaving as expected.

For

Visit the api/users/123 to confirm that the page doesn’t crash (this confirms the updated import logic here works as expected

It doesn’t crash but it returns a message Not found. Is that expected?

[ericapisani]

@nickytonline

It doesn’t crash but it returns a message Not found. Is that expected?

Yes that's correct. Prior to the logic introduced here, you would see a function crashing error rather than a 'not found'

[nickytonline]

Thanks for answering my questions @ericapisani! 🚀