feat: Add local filesystem cache for webpack5 subapp

[kylejeske]

Simple helper function for configuring webpack 5 filesystem cache with sensible defaults.

Features:

• Zero-config setup with createFilesystemCacheConfig(__filename)
• Automatic cache invalidation when webpack config changes
• Customizable cache directory, name, and version
• TypeScript support with full type definitions
• Framework-agnostic (works with any webpack 5 setup)

Usage:

// webpack.config.js

const { createFilesystemCacheConfig } = require('@xarc/webpack-devcache-config');

// other xarc/app-dev includes
const {
  initWebpackConfigComposer,
  compose,
  getComposeOptions,
} = require("@xarc/app-dev/config/webpack");

const options = getComposeOptions();
const { composer, ...opts } = initWebpackConfigComposer(options);

// other webpack config settings/options

const finalConfig = compose({ composer, ...opts });

// Enable filesystem cache for subapps
const isDev = process.env.NODE_ENV !== 'production';
if (isDev) {
  finalConfig.cache = createFilesystemCacheConfig(__filename);
  console.log('✅ [WEBPACK CACHE] Filesystem cache enabled with SubApp serialization support!');
}

Benefits:

• Reduces boilerplate for webpack cache configuration
• Ensures consistent cache setup across projects
• Works seamlessly with @xarc/webpack SubApp serialization support

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