Add os.version and os.features to platform spec

These changes are needed to differentiate Windows images.

Signed-off-by: John Starks <jostarks@microsoft.com>

docs/spec/manifest-v2-2.md

@@ -89,6 +89,17 @@ image manifest based on the Content-Type returned in the HTTP response.
             The os field specifies the operating system, for example
             `linux` or `windows`.
 
+        - **`os.version`** *string*
+
+            The optional os.version field specifies the operating system version,
+            for example `10.0.10586`.
+
+        - **`os.features`** *array*
+
+            The optional os.features field specifies an array of strings,
+            each listing a required OS feature (for example on Windows
+            `win32k`).
+
         - **`variant`** *string*
 
             The optional variant field specifies a variant of the CPU, for

manifest/manifestlist/manifestlist.go

@@ -47,11 +47,19 @@ type PlatformSpec struct {
 	// OS specifies the operating system, for example `linux` or `windows`.
 	OS string `json:"os"`
 
+	// OSVersion is an optional field specifying the operating system
+	// version, for example `10.0.10586`.
+	OSVersion string `json:"os.version,omitempty"`
+
+	// OSFeatures is an optional field specifying an array of strings,
+	// each listing a required OS feature (for example on Windows `win32k`).
+	OSFeatures []string `json:"os.features,omitempty"`
+
 	// Variant is an optional field specifying a variant of the CPU, for
 	// example `ppc64le` to specify a little-endian version of a PowerPC CPU.
 	Variant string `json:"variant,omitempty"`
 
-	// Features is an optional field specifuing an array of strings, each
+	// Features is an optional field specifying an array of strings, each
 	// listing a required CPU feature (for example `sse4` or `aes`).
 	Features []string `json:"features,omitempty"`
 }