Step 1: The Addressbook Counter Contract - missing step in CLI instructions

[interwebcoding]

File: [docs/02_getting-started/03_smart-contract-development/07_inline-action-to-external-contract.md](https://github.com/EOSIO/welcome/blob/develop/docs/02_getting-started/03_smart-contract-development/07_inline-action-to-external-contract.md)

Current:

cd CONTRACTS_DIR
mkdir abcounter
touch abcounter.cpp

Should be:

cd CONTRACTS_DIR
mkdir abcounter
cd abcounter
touch abcounter.cpp