Refactor packages (func name & UI) (#34773)

1. Use `OpenXxx` instead of `GetXxx` because the returned readers should
be correctly closed, and clarify the behaviors of the functions: they
increase the download counter
2. Use `packages-content` styles instead of `issue-content`

web_src/css/index.css

@@ -70,6 +70,7 @@
 @import "./repo/reactions.css";
 @import "./repo/clone.css";
 @import "./repo/commit-sign.css";
+@import "./repo/packages.css";
 
 @import "./editor/fileeditor.css";
 @import "./editor/combomarkdowneditor.css";