fix: Fix exports in VueFileHandler and GraphqlFileHandler

[unite4]

Fixes the problem with loading Kombinator plugins after latest release of jiti (https://github.com/unjs/jiti/releases/tag/v1.21.1).

[error] [mods-plugin] _VueFileHandler.VueFileHandler is not a constructor
[error] Nuxt Build Error: _VueFileHandler.VueFileHandler is not a constructor
  at node_modules/@creativestyle/kombinator/dist/vite-plugin-execute-mods.js:88:29
  at Array.forEach (<anonymous>)
  at processVueMods (node_modules/@creativestyle/kombinator/dist/vite-plugin-execute-mods.js:73:11)
  at Object.handler (node_modules/@creativestyle/kombinator/dist/vite-plugin-execute-mods.js:106:11)
  at node_modules/@nuxt/vite-builder/node_modules/rollup/dist/es/shared/node-entry.js:19774:40
  at async Promise.all (index 0)
  at async PluginDriver.hookParallel (node_modules/@nuxt/vite-builder/node_modules/rollup/dist/es/shared/node-entry.js:19702:9)
  at async node_modules/@nuxt/vite-builder/node_modules/rollup/dist/es/shared/node-entry.js:20609:13
  at async catchUnfinishedHookActions (node_modules/@nuxt/vite-builder/node_modules/rollup/dist/es/shared/node-entry.js:20119:16)
  at async rollupInternal (node_modules/@nuxt/vite-builder/node_modules/rollup/dist/es/shared/node-entry.js:20606:5)
  at async Module.build (node_modules/@nuxt/vite-builder/node_modules/vite/dist/node/chunks/dep-V3BH7oO1.js:67172:18)
  at async buildClient (node_modules/@nuxt/vite-builder/dist/shared/vite-builder.NwMCGWpb.mjs:569:5)
  at async bundle (node_modules/@nuxt/vite-builder/dist/shared/vite-builder.NwMCGWpb.mjs:1462:3)
  at async bundle (node_modules/nuxt/dist/index.mjs:4729:5)
  at async Promise.all (index 1)
  at async build (node_modules/nuxt/dist/index.mjs:4604:5)
  at async Object.run (node_modules/nuxi/dist/chunks/build.mjs:95:5)
  at async runCommand$1 (node_modules/nuxi/dist/shared/nuxi.9edf0930.mjs:1648:16)
  at async runCommand$1 (node_modules/nuxi/dist/shared/nuxi.9edf0930.mjs:1639:11)
  at async runMain$1 (node_modules/nuxi/dist/shared/nuxi.9edf0930.mjs:1777:7)