message: fix: link transferWithSignature and getTransferSignature
diff: @@ -503,6 +503,8 @@ matic.transferERC721Tokens('0x718Ca123...', user, '100006500000000000000', {
  ---
  +<a name="getTransferSignature"></a>
  +
  #### matic.getTransferSignature(toSell, toBuy)
  Off-chain signature generation for [transferWithSig](https://github.com/maticnetwork/contracts/blob/a9b77252ece25adcd3f74443411821883bb970e6/contracts/child/BaseERC20.sol#L35) function call
  @@ -543,6 +545,8 @@ Off-chain signature generation for [transferWithSig](https://github.com/maticnet
  ---
  +<a name="transferWithSignature"></a>
  +
  #### matic.transferWithSignature(sig, toSell, toBuy, orderFiller)
  Executes [transferWithSig](https://github.com/maticnetwork/contracts/blob/a9b77252ece25adcd3f74443411821883bb970e6/contracts/child/BaseERC20.sol#L35) on child token (erc20/721). Takes input as signature generated from `matic.getTransferSignature`
  