docs: add a new security assumption

Author: smol-ninja

SECURITY.md

@@ -42,6 +42,8 @@ Flow has been developed with the following additional assumptions:
 - There could be a minor discrepancy between the actual streamed amount and the expected amount. This is due to `rps`
   being an 18-decimal number, while users provide the amount per interval in the UI. If `rps` had infinite decimals,
   this discrepancy would not occur.
+- When withdrawing from multiple streams using `batch` function, the minimum fee required to execute the batch is equal to
+  the minimum fee required to withdraw from a single stream. This is intentional and expected behavior.
 
 ## Lockup
 
@@ -52,3 +54,6 @@ Sablier Lockup has been developed with the following additional assumptions:
 - There is no need for exponents greater than ~18.44 in `LockupDynamic` segments.
 - Recipient contracts on the hook allowlist have gone through due diligence and are assumed to expose no risk to the
   Sablier protocol.
+- When withdrawing from multiple streams either using `batch` or `withdrawMultiple` function, the minimum fee required to
+  execute the transaction is equal to the minimum fee required to withdraw from a single stream. This is intentional
+  and expected behavior.