Name of the SENDER_ADDRESS variable

[AndreasK24]

Reading the documentation about the Sender Contract (https://academy.avax.network/course/interchain-messaging/04-icm-basics/04-create-sender-contract) the environment variable "SENDER_ADDRESS" (otherwise the user could think, that the SENDER_ADDRESS is the wallet address of the user) should be called "SENDER_CONTRACT_ADDRESS" (otherwise the user could think, that the SENDER_ADDRESS is the wallet address of the user) and an additional description should be added, that this variable is the place where the contract got Deployed to.