Add Futurenet to Network Passphrases (#306)

docs/encyclopedia/network-passphrases.mdx

@@ -2,13 +2,14 @@
 title: Network Passphrases
 ---
 
-Stellar’s Pubnet and Testnet each have their own unique passphrase. These are used when validating signatures on a given transaction. If you sign a transaction for one network but submit it to another, it won’t be considered valid. By convention, the format of a passphrase is ‘`[Network Name] ; [Month of Creation] [Year of Creation]`’.
+Stellar’s Mainnet, Testnet, and Futurenet each have their own unique passphrase. These are used when validating signatures on a given transaction. If you sign a transaction for one network but submit it to another, it won’t be considered valid. By convention, the format of a passphrase is ‘`[Network Name] ; [Month of Creation] [Year of Creation]`’.
 
-The current passphrases for the Stellar Pubnet and Testnet are:
+The current passphrases for the Stellar Mainnet, Testnet, and Futurenet are:
 
-- Pubnet: '`Public Global Stellar Network ; September 2015`'
+- Mainnet: '`Public Global Stellar Network ; September 2015`'
 - Testnet: '`Test SDF Network ; September 2015`'
+- Futurenet: '`Test SDF Future Network ; October 2022`'
 
 Passphrases serve two main purposes: (1) used as the seed for the root account (master network key) at genesis and (2) used to build hashes of transactions, which are ultimately what is signed by each signer’s secret key in a transaction envelope; this allows you to verify that a transaction was intended for a specific network by its signers.
 
-Most SDKs have the passphrases hardcoded for the Stellar Pubnet and Testnet. If you’re running a private network, you’ll have to manually pass in a passphrase to be used whenever transaction hashes are generated. All of Stellar’s official SDKs allow you to use a network with a custom passphrase.
+Many SDKs have the passphrases hardcoded for Stellar's networks. If you’re running a private network, you’ll have to manually pass in a passphrase to be used whenever transaction hashes are generated. All of Stellar’s official SDKs allow you to use a network with a custom passphrase.