[Feature Request] Add Python module for detecting T1087.003

## 🐍 Python Module for MITRE ATT&CK Technique Detection

**Technique Name:** Account Discovery: Email Account

**Technique ID:** T1087.003

**Technique Description:** Adversaries may attempt to get a listing of email addresses and accounts. This internal identity enumeration can then be used to target further post-exploitation collection against accounts with placement and access to desired information.

Please ensure the following tasks are completed before submitting your feature request:

- [x] This issue is for a specific MITRE ATT&CK technique detection
- [x] The technique name and ID are clearly specified
- [ ] The problem and desired solution are clearly described
- [ ] Any necessary alternatives or additional context have been provided