Improve the docs homepage by adding workflows and personas to the blocks.

[johnnymatthews]

The current Filecoin Docs homepage tells the user what Filecoin is, a few interesting features of Filecoin, and where the reader can find the Lotus Docs. This layout was fine for an initial homepage, but we can do much better.

I propose that we treat this homepage as a way for users to navigate to certain parts of the documentation, depending on what they're trying to do:

• Just find out what Filecoin is → go to Basics/About section.
• Build dapps and smart-contracts → go to Developers Smart Contract section.
• Set up a storage provider → go to the Providers section.
• Store a bunch of data on Filecoin → go to the Store section.

Tasks

• [ ] ~Check in with the community/Filecoin devs to see if these use cases fit what we're expecting to see.~ Bumped to p1 by the FVM team. No time to check in with community.
• [x] Create a short paragraph for each use case.
• [x] Create a design to house each paragraph/block.
  • [x] Ensure it makes visual sense in a mobile view.
• [x] Add callout section towards the top of the page for hackathons/events/major updates.
• [ ] Optional: create visual aids/images for each use case.

[johnnymatthews]

As well as adding in sections for each use-case/persona, it'd be useful to have a Recent updates or just Updates section. This new section can tell readers what's changed in the docs recently, and what's happening in the wider Filecoin Network community. We can also add a Recent Blog Posts section to highlight the latest posts in the Filecoin Blog.

[johnnymatthews]

Bumping to P1 at the request of the FVM team.