docs: Add missing plugins to README

[yamz8]

Summary

Adds documentation for 8 plugins that were missing from the README but present in marketplace.json.

Changes

Plugins Added to Documentation

Remote MCP Servers (6):

• bioRxiv/medRxiv - Access to bioRxiv and medRxiv preprint data
• ChEMBL Database - Bioactive drug-like compounds database
• ClinicalTrials.gov - NIH/NLM clinical trials registry
• Open Targets Platform - Drug target discovery and prioritisation
• Owkin - AI agents for biology (HistoPLUS)
• Medidata - Clinical trial platform help and site ranking

Local MCP Servers (1):

• ToolUniverse - AI agents and tools for scientific discovery

Skills (1):

• Clinical Trial Protocol - Generate FDA/NIH-compliant protocols

Sections Updated

1. Quick Start - Added all missing plugin install commands
2. Available Plugins - Added detailed documentation sections for each plugin
3. Detailed Installation - Updated with complete plugin list
4. Authentication Requirements - Clarified authentication needs for all plugins

Consistency

• Followed existing documentation format
• Maintained consistent structure with other plugin entries
• Updated all relevant sections to ensure completeness
• Sourced descriptions from each plugin's plugin.json configuration

Testing

After merging, users should be able to:

• Discover all available plugins in the README
• Find accurate installation commands
• Understand authentication requirements
• Access complete plugin descriptions

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