* Add more gem metadata

Author: PikachuEXE

asset_sync.gemspec

@@ -40,5 +40,9 @@ Gem::Specification.new do |s|
   s.executables   = `git ls-files -- bin/*`.split("\n").map{ |f| File.basename(f) }
   s.require_paths = ["lib"]
 
-  s.metadata["changelog_uri"] = "#{s.homepage}/blob/master/CHANGELOG.md"
+  s.metadata = {
+    "bug_tracker_uri"   => "#{s.homepage}/issues",
+    "changelog_uri"     => "#{s.homepage}/blob/master/CHANGELOG.md",
+    "source_code_uri"   => s.homepage,
+  }
 end