[FIRST EPSS] Create playbook compatible internal enrichment connector

[Powlinett]

Proposed changes

• Copy and adapt internal enrichment template
• Check marking, scope and CVE format
• Get data from https://api.first.org/data/v1/epss
• Update x_opencti_epss_score and x_opencti_epss_percentile vulnerability properties
• Test playbook compatibility

Related issues

• resolves #2418

Checklist

• [x] I consider the submitted work as finished
• [x] I tested the code for its functionality using different use cases
• [ ] I added/update the relevant documentation (either on github or on notion)
• [x] Where necessary I refactored code to improve the overall quality

Further comments

I'm not sure about the documentation, feel free to tell me what I should add/fix 🤞