fix the bare url and the Summary of http://semver.org

Signed-off-by: yupengzte <[email protected]>

VENDORING.md

@@ -26,13 +26,14 @@ dependency on a package of a specific version or greater up to the next major
 release, without encountering breaking changes.
 
 ## Semantic Versioning
-Annotated version tags should follow Schema Versioning policies.
-According to http://semver.org:
+Annotated version tags should follow [Semantic Versioning](http://semver.org) policies:
 
 "Given a version number MAJOR.MINOR.PATCH, increment the:
-    MAJOR version when you make incompatible API changes,
-    MINOR version when you add functionality in a backwards-compatible manner, and
-    PATCH version when you make backwards-compatible bug fixes.
+
+   1. MAJOR version when you make incompatible API changes,
+   2. MINOR version when you add functionality in a backwards-compatible manner, and
+   3. PATCH version when you make backwards-compatible bug fixes.
+
 Additional labels for pre-release and build metadata are available as extensions
 to the MAJOR.MINOR.PATCH format."