docs: firebase functions coexistense

[vis97c]

Describe the feature

The way firebase deploy docs are paraphrased can mislead devs into thinking other functions cannot be deployed alongside nuxt.

According to firebase docs, multiple sources are supported.

// firebase.json
{
  "functions": [
    {
      "source": "functions",
      "codebase": "default",
      "ignore": [
        "node_modules",
        ".git",
        "firebase-debug.log",
        "firebase-debug.*.log"
      ],
      "predeploy": [
        "npm --prefix \"$RESOURCE_DIR\" run build"
      ]
    },
    {
      "source": ".output/server",
      "codebase": "nuxt"
    }
  ],
// ...more rules
}

Pls improve on that or let me know what steps to take. (not sure where in the codebase the deploy docs are managed)

E: this does also seems to affect nitro docs

Additional information

• Would you be willing to help implement this feature?
• Could this feature be implemented as a module?

Final checks

• Read the contribution guide.
• Check existing discussions and issues.

[atinux]

Happy to open a PR @vis97c ?