feat(github): add fetch document instructions (#370)

Author: 4t145

.github/instructions/fetch-mcp-doc.instructions.md

@@ -0,0 +1,74 @@
+---
+applyTo: '**'
+---
+
+When you need the information about the Model Context Protocol (MCP) specification, you can fetch the latest document from the official MCP website.
+
+# Overall
+#fetch https://modelcontextprotocol.io/specification/2025-06-18.md
+
+## Key Changes
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/changelog.md
+
+## Architecture
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/architecture.md
+
+# BaseProtocol
+## Overview
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/basic.md
+
+## Lifecycle
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/basic/lifecycle.md
+
+## Transports
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/basic/transports.md
+
+## Authorization
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/basic/authorization.md
+
+## Security Best Practices
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/basic/security_best_practices.md
+
+## Utilities
+### Cancellation
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/basic/utilities/cancellation.md
+
+### Ping
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/basic/utilities/ping.md
+
+### Progress
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/basic/utilities/progress.md
+
+# Client Features
+## Roots
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/client/roots.md
+
+## Sampling
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/client/sampling.md
+
+## Elicitation
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/client/elicitation.md
+
+# Server Features
+## Overview
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/server.md
+
+## Prompts
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/server/prompts.md
+
+## Resources
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/server/resources.md
+
+## Tools
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/server/tools.md
+
+## Utilities
+### Completion
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/server/utilities/completion.md
+### Logging
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/server/utilities/logging.md
+### Pagination
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/server/utilities/pagination.md
+
+# Schema Reference
+#fetch https://modelcontextprotocol.io/specification/2025-06-18/schema.md