Add version reference

Author: 0hsn

docs/05-References/052-version-reference.md

@@ -0,0 +1,46 @@
+---
+title: Version specification reference
+---
+
+:::note
+- This page should be use as reference for specification files.
+- This page is subject to change. It is requested to check this page frequently.
+:::
+
+### Introduction
+
+
+The Version specification format is how someone write a document version. Usually we encourage user to write document version on the very top of a specification document, so that you don't miss it. However it can be written as a top-level key on any place of the document. This is how it looks like:
+
+```yaml
+version: default:http:0.7.2
+...
+```
+
+Document version specifies which version of document current specification contents are written in. Simply think that, if someone wrote a document in a version that is not supported by the `chk` toolset currently installed: It will exit with an error. For example, if you run following in command-line:
+
+```bash
+$ chk
+Usage: ...
+
+  v0.2.0 | version strings: 0.7.2
+...
+```
+  - V0.2.0 is the tool version here
+  - 0.7.2 is the document version it supports
+
+If you have a document that have `version: default:http:0.8.0`, then this command would not be able to run it.
+
+### Format
+
+This version string have 3 parts: `<plugin>:<module>:<number>`, e.g: `default:http:0.8.0`
+
+- plugin: Name of the plugin that supports current specification. `default` means it part of core system. If you see other value it would mean you need to install that plugin to use the document.
+- module: A plugin can install multiple module on registration. So, `http` is the module name in `chk http ..`. Usually these are registered as sub-commands to `chk`.
+- number: the document version in [SEMVER](https://semver.org/) format.
+
+**`important`** This node have to be available on each document.
+
+### Support document versions:
+    - 0.7.2
+