Add MCP::Client#resource_templates to README

Author: sjrct

README.md

@@ -953,6 +953,7 @@ This class supports:
 - Tool listing via the `tools/list` method (`MCP::Client#tools`)
 - Tool invocation via the `tools/call` method (`MCP::Client#call_tools`)
 - Resource listing via the `resources/list` method (`MCP::Client#resources`)
+- Resource template listing via the `resources/templates/list` method (`MCP::Client#resource_templates`)
 - Resource reading via the `resources/read` method (`MCP::Client#read_resources`)
 - Prompt listing via the `prompts/list` method (`MCP::Client#prompts`)
 - Prompt retrieval via the `prompts/get` method (`MCP::Client#get_prompt`)