feat(dev): support PostCSS and Tailwind by default

[markdalgleish]

In Remix v2, PostCSS and Tailwind are supported by default if the relevant config files are present in the project. Consumers can opt out if this behaviour is undesired.

This PR also removes the unstable future flags.

[changeset-bot]

🦋 Changeset detected

Latest commit: e59aec4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 18 packages

Name	Type
@remix-run/dev	Major
create-remix	Major
remix	Major
@remix-run/architect	Major
@remix-run/cloudflare	Major
@remix-run/cloudflare-pages	Major
@remix-run/cloudflare-workers	Major
@remix-run/css-bundle	Major
@remix-run/deno	Major
@remix-run/eslint-config	Major
@remix-run/express	Major
@remix-run/netlify	Major
@remix-run/node	Major
@remix-run/react	Major
@remix-run/serve	Major
@remix-run/server-runtime	Major
@remix-run/testing	Major
@remix-run/vercel	Major

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[github-actions]

🤖 Hello there,

We just published version v0.0.0-nightly-44db74a-20230724 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

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[github-actions]

🤖 Hello there,

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[github-actions]

🤖 Hello there,

We just published version 1.19.2-pre.1 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!

[github-actions]

🤖 Hello there,

We just published version v0.0.0-nightly-7cb1e7e-20230803 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!

[github-actions]

🤖 Hello there,

We just published version 1.19.2-pre.2 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!

[github-actions]

🤖 Hello there,

We just published version v0.0.0-nightly-6e250f7-20230805 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!

[github-actions]

🤖 Hello there,

We just published version v0.0.0-nightly-b1149bb-20230810 which includes this pull request. If you'd like to take it for a test run please try it out and let us know what you think!

Thanks!