docs(contributing-md): add lerna example on npm dependencies

Signed-off-by: Peter Somogyvari <[email protected]>

CONTRIBUTING.md

@@ -17,7 +17,6 @@ As a developer:
 
 To protect the Hyperledger Cactus source code, GitHub pull requests are accepted from forked repositories only. There are also quality standards identified and documented here that will be enhanced over time.
 
-
 1. Fork [hyperledger/cactus](https://github.com/hyperledger/cactus) via Github UI
 1. Clone the fork to your local machine
 1. Complete the desired changes and where possible test locally (more detail to come here)
@@ -27,3 +26,13 @@ To protect the Hyperledger Cactus source code, GitHub pull requests are accepted
 1. Push your changes to your master
 1. Initiate a pull request from your fork to the base repository
 1. Await CI, DCO & linting quality checks, as well as any feedback from reviewers
+
+### Adding a new dependency to one of the packages:
+
+For example web3 can be added as a dependency to the besu ledger connector plugin's package this way:
+
+```sh
+npx lerna add web3@latest --scope '*/*plugin-ledger-connector-besu' --exact # [--dev] [--peer]
+```
+
+If you are adding a development dependency you can use the `--dev` option and `--peer` for a peer dependency.