Currently when doing the fund action on ploygon it will raise issue when the number is big than 9007199254740991(2**53 -1), it is because ethers.utils.hexlify function will check the number and if this is not a safe js integer, it will raise the issue.
However since the decimal of MATIC is 18, it will really easy the number is bigger than 2 **53. This PR is to fix the issue by using the bignumber instead of javascript number.
Currently when doing the fund action on ploygon it will raise issue when the number is big than 9007199254740991(2**53 -1), it is because
ethers.utils.hexlifyfunction will check the number and if this is not a safe js integer, it will raise the issue.However since the decimal of MATIC is 18, it will really easy the number is bigger than 2 **53. This PR is to fix the issue by using the bignumber instead of javascript number.