Add codex config sample into docs

[savinmikhail]

Hi!

I added “Running on Codex CLI” section to help users configure this MCP server in Codex.

Changes

• Updated README.md:101 with Codex CLI configuration

[ccbbccbb]

Tested with my own config.toml and works. This CLI command also does the job - however end result is slightly different.

# replace with actual firecrawl api key
codex mcp add firecrawl --env FIRECRAWL_API_KEY=fc-YOUR_API_KEY-- npx -y firecrawl-mcp

& the output in config.toml is slightly different (.env on 2 extra lines), but still works.

[mcp_servers.firecrawl]
command = "npx"
args = ["-y", "firecrawl-mcp"]

[mcp_servers.firecrawl.env]
FIRECRAWL_API_KEY = "fc-YOUR_API_KEY"

@savinmikhail I can make a PR to merge this CLI command into your branch.

[savinmikhail]

@ccbbccbb hi, yep, go ahead, i'll appreciate your help