refactor(core): cleaner _dist folder generation

[ojvribeiro]

Resolves #28.

The _dist folder should be deploy-ready, so making it cleaner allows the dev to simply upload its contents via FTP or via a CI/CD pipeline.

The folder structure should look like this:

📦_dist
 ┣ 📂assets
 ┃ ┣ 📂css
 ┃ ┣ 📂img
 ┃ ┗ 📂_vulmix
 ┃ ┃ ┣ 📂css
 ┃ ┃ ┗ 📂js
 ┗ 📜index.html