feat(plugin-router): add esbuild plugin

[benmcginnis]

Addresses #2576 by adding an esbuild plugin to the router-plugin package.

Duplicated the basic-file-based e2e test to verify validate the behavior, and replaces the vite config with an esbuild config as well as replacing the vite scripts with esbuild scripts.

tested by running: pnpm run test:e2e from within the e2e/react-router/basic-esbuild-file-based directory.