Docs - Set up new SDK structure

[hieronx]

Set up new docs structure:

Centrifuge SDK

• Overview
• Guides
  => Invest into a vault
  => Query data of a pool (to be added later: Docs - Add Query data of a pool page #193)
  => Buying/selling DeFi assets (to be added later: Docs - Add Buying/selling DeFi assets page #194)

Overview page

Similar to https://docs.centrifuge.io/developer/centrifuge-sdk/overview/

But as simple as possible (i.e. remove default parameters, focus on connecting to mainnet, etc)

Invest into a vault page

Similar structure as https://docs.centrifuge.io/developer/protocol/guides/invest-into-a-vault/, but using the SDK

Add prerequisities and install step like on https://docs.safe.global/sdk/starter-kit/guides/send-transactions