Refactoring Sygma docs

[haochizzle]

refactor:

• larger restructure for docs to add sections for devs, for users, for cross-chain apps, relayers etc.
• add tailored security documentation
• add relevant details for how relayers work under spectre vs zipline verification
• add documentation for tailored security - selection mechanism
• add documentation for btc
• add documentation for cross-chain app multichain-deploy
• add documentation for widget
• add documentation for validator-app

chores:

• update github repositories to include new repos
• update audits page to include veridise report
• update FAQs to include tailored security resources
• update examples to use cronos testnet where applicable
• update video resources to include new substrate workshop
• remove testnet faucet links (e.g. resources->official links page)
• update glossary to include terms related to tailored security
• update dictionary

closes:[#134][#142]

[MakMuftic]

Minor remarks:

• we should add a widget URL on the landing page (What's Next)
• on the /protocol page first, arh. diagram should be centered IMO
• Not sure do we need Using The Sygma UI Widget as we have a dedicated widget part in Integrating With Sygma