added versioning

Author: mtrezza

CONTRIBUTING.md

@@ -19,6 +19,7 @@
     - [Wording Guideline](#wording-guideline)
   - [Parse Error](#parse-error)
   - [Parse Server Configuration](#parse-server-configuration)
+- [Versioning](#versioning)
 - [Code of Conduct](#code-of-conduct)
 
 ## Contributing
@@ -281,6 +282,13 @@ Introducing new [Parse Server configuration][config] parameters requires the fol
 1. Add test cases to ensure the correct parameter value validation. Parse Server throws an error at launch if an invalid value is set for any configuration parameter.
 1. Execute `npm run docs` to generate the documentation in the `/out` directory. Take a look at the documentation whether the description and formatting of the newly introduced parameters is satisfactory.
 
+## Versioning
+
+Parse Server follows [semantic versioning](https://semver.org) with syntax `x.y.z` which defines:
+- `x` is the *major* version number which means a *breaking release* that may include changes that are not backwards compatible
+- `y` is the *minor* version number which means a *feature release* that may include new features, improvements or other changes that are backwards compatible
+- `z` is the *patch* version number which means a *patch release* that may include bug fixes that are backwards compatible
+
 ## Code of Conduct
 
 This project adheres to the [Contributor Covenant Code of Conduct](https://github.com/parse-community/parse-server/blob/master/CODE_OF_CONDUCT.md). By participating, you are expected to honor this code.