feat: support tailwind v4

[heddendorp]

PR Checklist

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• The commit message follows our guidelines: https://github.com/angular/angular-cli/blob/main/CONTRIBUTING.md#-commit-message-guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

The current integration if for tailwind V3 only.

Issue Number: #28938

What is the new behavior?

Detect if tailwind v4 is used as indicated by the presence of the @tailwindcss/postcss package. If so, check that also tailwindcss is installed. If both are present, Add the tailwind postCSS plugin.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[pumano]

would be good to have same support for esbuild builder too, not only for webpack

[heddendorp]

would be good to have same support for esbuild builder too, not only for webpack

Agreed, I found what seems to be the correct place here https://github.com/angular/angular-cli/pull/28939/files#diff-c31d390b8683db112fcc30e2ee984d893bdce6bd8e6d7d70c43ecc410a626a3dR489
But I am unsure how to add it correctly for the application builder.

[clydin]

would be good to have same support for esbuild builder too, not only for webpack

The application build system supports custom postcss configuration via either a postcss.config.json or .postcssrc.json file. Note that this can lead to increased build times since postcss is otherwise unused in the application build system and is only enabled if tailwind and/or a postcss configuration file is present.