Update README.md

[djhaynes]

• Updated lists to start a 1 rather than 0. In other areas of the GitHub repo and lab documentation, we start lists at 1.
• Removed "ATT&CK" from "ATT&CK Adversary Emulation" since redundant because we preface it with "MITRE ATT&CK Defender".
• Updated VM setup scripts directory and script file names to align with what's in GitHub.
• Some other very minor changes.