Mention target in publish info message

[amvanbaren]

Use extension.targetPlatform instead of options.target.

The logging format follows the same pattern as other parts of the codebase: https://github.com/eclipse/openvsx/blob/df28c16c4d919afaf1c8795ab0dfabd842ceb6e6/cli/src/get.ts#L106-L107 https://github.com/eclipse/openvsx/blob/df28c16c4d919afaf1c8795ab0dfabd842ceb6e6/server/src/main/java/org/eclipse/openvsx/ExtensionService.java#L190-L193

cc @radeksimko