Update documentation

[turbolent]

Context

New features have been added to Cadence in the last few releases.
Update the documentation and describe the new features

Definition of Done

• Querying block information

  • Get the current block:
    fun getCurrentBlock(): Block

  • Get a block at a given height:
    fun getBlock(at height: UInt64): Block?

  • The block info is:

    struct Block {
        let id: [UInt8; 32]
        let height: UInt64
        let timestamp: UFix64
    }
    

  • Also update https://docs.onflow.org/docs/faq#how-do-i-access-block-information-like-timestamp-and-block-number-in-cadence

• Crypto contract
• Typed capabilities
• Run-time Types
• Addresses size (8 instead of 20 bytes)
• Parameters for transactions and scripts
• fun toString(): String was added for all number types and addresses
• fun toBytes(): [UInt8] was added to Address
• fun toBigEndianBytes(): [UInt8] was added to all number types.
• Fields which have a non-storable type are now rejected:
  Non-storable types are:
  • Functions (e.g. ((Int): Bool))
  • Accounts (AuthAccount / PublicAccount)
  • Transactions
  • Void
• String.decodeHex(): [Int] → String.decodeHex(): [UInt8]
• AuthAccount.addPublicKey(publicKey: [Int]) → AuthAccount.addPublicKey(publicKey: [UInt8])
• AuthAccount.setCode(code: [Int]) → AuthAccount.setCode(code: [UInt8])
• Conformance check now allows subtype for return type
• Type hierarchy
• unsafeRandom
• Account creation

[timmymmit]

Add section for Roadmap and Features that are upcoming