docs(mcp): add .mcp.json config examples earlier in MCP docs

## Description

The MCP Getting Started section at https://redis-field-engineering.github.io/redisctl-docs/mcp/#getting-started should include `.mcp.json` configuration examples earlier in the flow, so users can see concrete config snippets before diving into usage.

## Location

`docs/docs/mcp/index.md` and/or `docs/docs/mcp/getting-started.md`