Use errors.New() to output the error message and fix some typos

Signed-off-by: fate-grand-order <chenjg@harmonycloud.cn>

blobs.go

@@ -152,7 +152,7 @@ type BlobProvider interface {
 
 // BlobServer can serve blobs via http.
 type BlobServer interface {
-	// ServeBlob attempts to serve the blob, identifed by dgst, via http. The
+	// ServeBlob attempts to serve the blob, identified by dgst, via http. The
 	// service may decide to redirect the client elsewhere or serve the data
 	// directly.
 	//