Add Wrapped MATIC to WETH9 addresses

[georgeroman]

This will result in consistent handling of the wrapped native currency on Polygon which uses MATIC instead of ETH: https://github.com/Uniswap/sdk-core/blob/be6b14fa6f9223e0483389d792a9e07eab557a27/src/entities/weth9.ts#L6

[Florian-S-A-W]

@georgeroman I agree that this makes sense. I created a pull request to resolve this.

[ashutosh887]

I would like to work on this @Florian-S-A-W @georgeroman