The user send his NFT to Escorw contract with send message (which is basic function of cw721 base contract).
-Options
1.Set the expiration time for escrow.
2.Set the recipient for the NFT.
3.Set the price of NFT.
-Check if the sent money from recipeint to the escrow contract is the same as the amount of fund which the
source user set
-Validate the expiration time.
If the expiration is finished, the source user can withdraw his NFT.