Create docs.page documentation

[renefloor]

🏗 Enhancement Proposal

Create a docs.page documentation website. It is really easy to create documentation that way.

Current progress can be tracked here: docs.page documentation

[ ] Basic usage (placeholder, error, etc)
[ ] Testing
[ ] Using Firebase
[ ] Custom caching rules
[ ] Memory usage (e.g. Image size)
[ ] Update files in cache

[orestesgaolin]

Would love to see how to provide custom http client (e.g. with authenticated headers) to fetch images. E.g. example showcasing dio or other http alternative would be useful.