update the 'user-guide.md'

Author: dd-jy

docs/user-guide.md

@@ -151,5 +151,5 @@ For a unique OSS name, OSS name is printed such as (package_manager):(oss name)
 | Npm             | npm:(oss name)     | Priority1. repository in package.json <br> Priority2. www.npmjs.com/package/(oss_name) | www.npmjs.com/package/(oss_name) |
 | Pip             | pypi:(oss name)    | https://pypi.org/project/(oss_name)/(version) | homepage in (pip show) information |
 | Maven (Gradle) | (group_id):(artifact_id) | https://mvnrepository.com/artifact/(group_id)/(artifact_id)/(version) | https://mvnrepository.com/artifact/(group_id)/(artifact_id) |
-| Pub             | (oss name)         | homepage in (pub information) | homepage in (pub information) |
+| Pub             | pub:(oss name)         | https://pub.dev/packages/(oss_name)/versions/(version) | homepage in (pub information) |