Docs: Firebase Preset improvements

[luc122c]

Describe the feature

I tried implementing the new Gen2 preset, and noticed there were a couple of inconsitencies between the code, and the docs. I'll open a PR to fix them, but wanted to note them down here:

• Node version expects a string, it's a number in the docs.
• In Options httpOptions should be httpsOptions

Example: https://stackblitz.com/edit/nuxt-starter-jnm8wc?file=nuxt.config.ts

Additional information

• Would you be willing to help implement this feature?