Add Vite 8 support, BoxLang layout paths, and comprehensive docs

[lmajano]

• Bump version to 4.0.0
• Update peerDependencies to include Vite 7 and 8
• Update devDependencies: vite ^8.0.0, esbuild ^0.28.0
• Add appRefreshPaths export for BoxLang / tiered app layout
  (app/layouts/, app/views/, app/config/Router.bx)
• Guard chunk.viteMetadata?.importedCss in renderChunk for Rolldown
  compatibility (Vite 8 may not set viteMetadata on every chunk)
• Replace Manifest import from vite with a local type definition to
  avoid breakage if Vite renames the type in future versions
• Replace any-typed renderChunk chunk param with ViteChunk interface
• Fix resolveManifestConfig fallback to use .vite/manifest.json
  (Vite 5+ default) instead of manifest.json
• Add package.json "type": "module" to support ESM eslint.config.js
• Migrate ESLint config from .eslintrc.js to eslint.config.js (flat
  config, required for ESLint 9)
• Update CI Node versions: 14/16/18 -> 18/20/22; upgrade actions to v4
• Rewrite README with full documentation: both layout configurations,
  configuration reference table, refresh paths, aliases, SSR, Inertia,
  env vars, and framework integration examples
• Add tests for appRefreshPaths, BoxLang layout outDir, and refresh
  with appRefreshPaths (29 tests total, all passing)