v0.20: A lot of new stuff

• New TonRecipes.NFTs added to work with TEP-62 NFTs: GetCollectionData, GetNftAddressByIndex, GetNftData, GetNftContent, CreateTransferMessage;
• New extension methods ToBoc() for StackEntry, StackEntryCell, StackEntrySlice, Cell and Slice, so you can write shorter code with less ToTvmCell() and similar chained conversions;
• New extension methods ToInt(), ToLong(), ToBigInteger() and ToBigIntegerBytes() for StackEntry, so you can write result.Stack[0].ToInt() instead of int.Parse(result.Stack[0].ToTvmNumberDecimal(), CultureInfo.InvariantCulture);
• Additional constructors for types that expect List<ofSomething>: now they also accepts arrays with params modifier;
• New TonUtils.KeyUtils to work with keys, particularly ParseEd25519PublicKey to convert public key from internal tonlib representation to bytes;
• New requests: GetConfigAll and GetConfigParam to get blockchain configuration data;
• Additional Slice numeric methods: PreloadUShort, PreloadShort, PreloadUInt, PreloadInt, PreloadULong, PreloadLong;
• Additional Slice and CellBuilder string methods: LoadString and StoreString (as utf-8 bytes);
• Additional Slice and CellBuilder long-string methods: LoadStringSnake and StoreStringSnake, LoadStringChunked and StoreStringChunked;
• Support for wallet-v4: V4AccountState and V4InitialAccountState;
• New framework net8.0 added to list of target frameworks