message: chg: update README for examples
diff: git clone git@github.com:maticnetwork/matic.js.git
  ```
  -
  -
  ### Edit config.js
  +
  ```
  PRIVATE_KEY: '<paste your private key here>', // A sample private key prefix with `0x`
  FROM_ADDRESS: '<paste address belonging to private key here>',// Your address
  ```
  +
  Update following lines with your wallet address and key.
  Be careful with your private key, Use a key your are comfortable with for development purpose.
  @@ -24,3 +24,4 @@ Be careful with your private key, Use a key your are comfortable with for devel
  cd examples/node
  npm install
  node balance-of-ERC20.js
  +```
  