add note to README about avoiding plugin execution on build

[nathanhannig]

The @vitejs/plugin-basic-ssl plugin is only needed for local development. However, if added normally to vite.config.js.

Please add a quick note to the README showing users how to stop this by using Vite's apply: 'serve' property.

import { defineConfig } from 'vite';
import basicSsl from '@vitejs/plugin-basic-ssl';

export default defineConfig({
  plugins: [
    {
      ...basicSsl(),
      apply: 'serve' // Prevents running during production builds
    }
  ]
});