Add 78 automation skills to marketplace.json

Adds all Composio/Rube MCP automation skills to the Claude Code plugin
marketplace for improved discoverability. Total plugins: 107 (29 existing + 78 automation).

Skills span 20 categories: CRM, project management, communication, email,
DevOps, storage, spreadsheets, calendar, social media, support, e-commerce,
design, analytics, HR, and automation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>