chore: optimise webpack config for examples

[webdiscus]

Hello @ankurk91,

I'm using your awesome component and have optimized the Webpack config for myself.
Now I would like to share an improved configuration.

Before merging try please my forked branch:

git clone https://github.com/webdiscus/demo-vue-flatpickr-component.git
cd demo-vue-flatpickr-component
npm i
npm run build
npm start

Note: file-loader is deprecated in Webpack 5, use the type: 'asset/resource' instead of file-loader

[webdiscus]

the syntax of the entry plugin option is the same as original webpack entry.
The key of the entry object is the output file w/o .html extension.
For example:

'index': './examples/index.html', // => saves to "docs/index.html"
'about/index':  './examples/about.html', // => saves to "docs/about/index.html"