feature(cli): add reactStrictMode option

[stipsan]

Description

Adds an option to sanity.cli.js that controls wether strict mode is enabled. It was previously always-on. Now it's opt-in. The test studio enables it by default.
Prior art: https://nextjs.org/docs/api-reference/next.config.js/react-strict-mode

How to disable strict mode in the test studio without editing renderStudio.tsx or dev/test-studio/sanity.cli.ts

Either run the dev command with an env var override:

SANITY_STUDIO_REACT_STRICT_MODE=false yarn dev

Or run this once and carry on as usual:

cp dev/test-studio/.env.example dev/test-studio/.env.development

Double console log calls

If you're seeing double console logs after enabling strict mode, check the Hide logs during second render in Strict Mode option in the React Devtools Components Settings modal:

What to review

In studios that have a sanity.cli.ts file, add reactStrictMode: true to enable it.
In studios without, it should be possible to opt-in by either SANITY_STUDIO_REACT_STRICT_MODE=true sanity start or by creating a .env.development file adjacent to sanity.config.ts with the same env var.
Other studios shouldn't see strict mode on.
Including custom studios that call renderStudio directly.

Notes for release

You can opt-in to React's Strict Mode checks for your custom studio components in these ways:

• Add reactStrictMode: true to your sanity.cli.ts file.
• Create a .env.development file and add SANITY_STUDIO_REACT_STRICT_MODE=true to it.
• Set the env var while starting sanity: SANITY_STUDIO_REACT_STRICT_MODE=true sanity start

We strongly suggest you opt-in to better prepare your custom studio for the future of React. This only affects development mode, production mode or sanity build is unaffected by this setting.

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Name	Status	Preview	Comments	Updated
test-studio	✅ Ready (Inspect)	Visit Preview	💬 Add your feedback	Oct 5, 2022 at 4:34AM (UTC)

1 Ignored Deployment

Name	Status	Preview	Comments	Updated
studio-workshop	⬜️ Ignored (Inspect)			Oct 5, 2022 at 4:34AM (UTC)

[snorrees]

Some nice info in the description here 👍

Only have one suggestion: add a period in the last sentence of Notes for release. I read it as "only affects development mode, production mode ... ie as a list of things it affects.

"This only affects development mode. Production mode or sanity build is unaffected by this setting."