Add versioning structure to help translations keep the project up-to-date

[vbrazo]

This PR suggests a versioning structure for V by example.

Issue

Closes #163

A Note on Example Versions

All examples should include the following header:

---
version: 3.5.1
example_title: JSON
---

Change the version attribute according to the following rules:

• MAJOR — You (re)wrote the whole thing. Your new content will need some translation.
• MINOR — Added or removed some content, few sentences, etc.
• PATCH — Spelling, typos. Probably not translated stuff.

We follow SemVer.org pattern. This is important because we use that to determine and inform translators of new content that requires translation.

[Delta456]

Looks good