Merge pull request #665 from bertux/patch-1

Update README.md to add missing --save-dev

README.md

@@ -84,7 +84,7 @@ Note: Address will vary if contract code is changed or a different Solidity vers
 
 Some networks require replay protection, making it incompatible with the default deployment process as it relies on a presigned transaction without replay protection (see https://github.com/Arachnid/deterministic-deployment-proxy). 
 
-Safe contracts use a different deterministic deployment proxy (https://github.com/safe-global/safe-singleton-factory). To make sure that the latest version of this package is installed, make sure to run `npm i @gnosis.pm/safe-singleton-factory` before deployment. For more information, including how to deploy the factory to a new network, please refer to the factory repo.  
+Safe contracts use a different deterministic deployment proxy (https://github.com/safe-global/safe-singleton-factory). To make sure that the latest version of this package is installed, make sure to run `npm i --save-dev @gnosis.pm/safe-singleton-factory` before deployment. For more information, including how to deploy the factory to a new network, please refer to the factory repo.  
 
 Note: This will result in different addresses compared to hardhat's default deterministic deployment process.