Add small introduction for each package

[ericfennis]

For the introduction page we want to explain the dev for how you can use lucide. So small introduction how you can implement svgs and list all the different packages and what they can accomplish.

The branch I work on: https://github.com/ericfennis/lucide/tree/feature/add-docs-to-site The document I already created: https://github.com/ericfennis/lucide/blob/feature/add-docs-to-site/docs/index.md. The current document I created is copy and pasted from the main README.md, but tells more how you install it not what is can do, so tell more how you can use it.