Add asset script transform hooks

[swernerx]

Adds a public, ordered script transform hook to @remix-run/assets so integrations can transform browser-delivered application source without wrapping or proxying the asset server.

• Adds scripts.transforms, which runs before Remix lowers TypeScript and JSX
• Provides each transform with the absolute file path, public URL pathname, source format, dependency status, and current source map
• Composes returned source maps with earlier transforms and the existing Oxc/minifier pipeline
• Registers returned watchFiles with the existing module cache and watcher invalidation flow
• Transforms symlinked npm, pnpm, and Yarn workspace packages by default while skipping installed or copied dependencies unless includeDependencies is enabled
• Documents the API and adds package/remix change notes

Closes #11580.

import { createAssetServer } from 'remix/assets'
import { compileMessages } from './app/compile-messages.ts'

let assetServer = createAssetServer({
  basePath: '/assets',
  fileMap: {
    '/app/*path': 'app/*path',
    '/npm/*path': 'node_modules/*path',
  },
  allowFiles: ['app/assets/**'],
  allowPackages: ['remix'],
  sourceMaps: 'external',
  scripts: {
    transforms: [
      {
        name: 'messages',
        async transform(code, context) {
          if (context.format !== 'tsx') return null

          let result = await compileMessages(code, {
            filePath: context.filePath,
            format: context.format,
          })
          return {
            code: result.code,
            sourceMap: result.sourceMap,
            watchFiles: result.dependencies,
          }
        },
      },
    ],
  },
})