[v1] docs should showcase alternative mesh configs without defineConfig

[enisdenjo]

When running mesh-serve with npx (or the future single-bin mesh-serve), the defineConfig (or any other export) is not available. In such cases, defining the config should be something like:

// mesh.config.ts

import type { MeshServeCLIConfig } from '@graphql-mesh/serve-cli';

export const serveConfig = {
  supergraph: 'hi.graphql',
} satisfies MeshServeCLIConfig;

or no type

// mesh.config.js

export const serveConfig = {
  supergraph: 'hi.graphql',
};