Move to monorepo structure

[MrSunshyne]

The current project structure is an astro project at the root directory

Proposal

Move everything related to astro from the root / directory to /packages/frontend-astro
All non-astro related stuff should move to /packages/common such as data fetching logic

/ -> /packages/frontend-astro
/ -> /packages/common

Motivation

This allows us to experiment with alternative frameworks while not losing the history of this repository.
The common package could then be consumed by the different frameworks, i.e currently astro, in the future, nuxt3.