feat(message-buffer): add .env.pythnet for message buffer init script (#889)

pythnet/message_buffer/scripts/.env.pythnet

@@ -0,0 +1,9 @@
+MESSAGE_BUFFER_PROGRAM_ID=7Vbmv1jt4vyuqBZcpYPpnVhrqVe5e6ZPb6JxDcffRHUM
+PAYER_KEYPAIR_PATH=<ABSOLUTE_PATH_TO_KEYPAIR>
+CLUSTER=pythnet
+# Whitelist admin will be initialized to same as payer
+# then a separate txn will be used to set it to the following address
+# after the message buffers have been initialized
+# WHITELIST_ADMIN=AmqEnGN76cdRYqNUFg44hX47iXwxRqoGsmNZR29UEGJB # Price feed multisig authority
+# 522 + 85(PriceFeedMessage) + 101(TwapMessage) + extra buffer
+INITIAL_SIZE=2048