docs: add discord link (#463)

Author: forcodedancing

docs/bnb-smart-chain/developers/faucet.md

@@ -16,9 +16,10 @@ To get some tBNB of BSC testnet for testing purposes, you can use the [online fa
 
 
 ## Claim tBNB from Discord
-1. Visit the BNB Chain Discord [faucet channel](https://discord.com/channels/789402563035660308/1099937267021250560)
-2. Type `/faucet {your receiver account}` and sent.
-3. You will receive **0.3 tBNB** in few seconds.
+1. Join the [BNB Chain Discord](https://discord.com/invite/bnbchain)
+2. Visit the BNB Chain Discord [faucet channel](https://discord.com/channels/789402563035660308/1099937267021250560)
+3. Type `/faucet {your receiver account}` and sent.
+4. You will receive **0.3 tBNB** in few seconds.
 
 *You can only claim once in 24 hours.*