Add webpack config to create a module bundle to be used with importmap

[vincentfretin]

Description:

Add webpack config to create a module bundle to be used with importmap

Changes proposed:

• Move shared config in webpack.common.js
• Create new webpack.module.config.js and npm run dist:module command

After merge, please commit the new bundle:

npm run dist
git add dist/aframe-master.module.min.js dist/aframe-master.module.min.js.map
git commit -m"Add new module bundle"

[dmarcos]

Thanks!