Add Hermes Tweet skill

[kriptoburak]

Adds Hermes Tweet as a native SkillHub automation skill for Hermes Agent X/Twitter workflows.

What changed:

• Adds skills/automation/hermes-tweet.md with install, configuration, read-only usage, action gating, troubleshooting, and references.
• Regenerates index.json so the skill appears in the registry.

Duplicate checks:

• Checked current repo contents for Hermes Tweet, hermes-tweet, Xquik, XQUIK_API_KEY, HERMES_TWEET, tweet, and Twitter references.
• Checked open and closed PRs/issues for Hermes/Xquik/tweet/Twitter matches. No existing Hermes Tweet submission found.

Validation:

• python3 scripts/validate_skill.py skills/automation/hermes-tweet.md passed with one existing parser warning about numbered step subsections. The skill uses ### 1. style headings; the validator appears to split the steps section before ### headings.
• python3 scripts/generate_index.py passed and indexed hermes-tweet.
• git diff --check passed.
• Added-line secret scan passed.
• Reference links checked HTTP 200 for Hermes Tweet, Hermes Agent plugin docs, Build a Hermes Plugin, and Xquik.