Update SWC-119.md

EthTrust reference

Author: chaals

entries/docs/SWC-119.md

@@ -31,6 +31,10 @@ Review storage variable layouts for your contract systems carefully and remove a
 - [Issue on Solidity's Github - Shadowing of inherited state variables should be an error (override keyword)](https://github.com/ethereum/solidity/issues/2563)
 - [Issue on Solidity's Github - Warn about shadowing state variables](https://github.com/ethereum/solidity/issues/973)
 
+### EEA EthTrust Security Levels Specification
+
+- [**[Q] Implement as Documented**](https://entethalliance.org/specs/ethtrust-sl/#req-3-implement-as-documented)
+
 ## Samples
 
 ### ShadowingInFunctions.sol