docs: add README file in spanish

[Villanuevand]

Checklist

• Issue number for this PR: Not found
• Docs included?: (yes)
• • README_es.md
• • install-and-setup_es.md
• Test units included?: (no)

Description

In this PR Im adding the README_es.md which is a copy of README.md translated to Spanish. I would like to translate the full documentation to spanish progressively

Code sample

None

[Villanuevand]

@jamesdaniels Just a heads up, Im taking back the work with this issue.

[Villanuevand]

List of docs to translate:

• [x] Quickstart Commit: e12c835
• [x] Upgrading to v7.0? Check out our guide Commit: 6aa203f
• [x] Getting started with Google Analytics Commit: d6abd13
• [ ] Documents
• [ ] Collections
• [ ] Querying Collections
• [ ] Offline data
• [ ] Objects
• [ ] Lists
• [ ] Querying lists
• [ ] Getting started with Firebase Authentication
• [ ] Route users with AngularFire guards
• [ ] Getting started with Firebase Emulator Suite
• [ ] Getting started with Cloud Storage
• [ ] Getting started with Firebase Messaging
• [ ] Getting started with Callable Functions
• [ ] Deploy your application on Firebase Hosting
• [ ] Getting started with Angular Universal
• [ ] Deploying your Universal application on Cloud Functions for Firebase
• [ ] Prerendering your Universal application
• [ ] Installation and Setup with Ionic CLI
• [ ] Using AngularFire with Ionic 2
• [ ] Using AngularFire with Ionic 3

Probably we are missing some nested docs.