spec: add spec for notation version command

specs/commandline/version.md

@@ -0,0 +1,41 @@
+# notation version
+
+## Description
+
+Use `notation version` to print notation version information.
+
+Upon successful execution, the following information is printed.
+
+```text
+Notation: Notary v2, A tool to sign, store, and verify artifacts.
+
+Version:    <MAJOR.MINOR.PATCH>
+```
+
+## Outline
+
+```text
+Print the notation version information
+
+Usage:
+  notation version [flags]
+
+Flags:
+  -h, --help          Help for version
+```
+
+## Usage
+
+### Print notation version information
+
+```shell
+notation version
+```
+
+An example output:
+
+```text
+Notation: Notary v2, A tool to sign, store, and verify artifacts.
+
+Version:    1.0.0
+```