CatalogItem: Align item in Sources to be vertically aligned

[brianabdl]

Catalog Items that are vertically aligned to the center rather than top aligned can make the user less confused about the install button when installing their choice of extension source.

I've also made a few behavior changes, when the user clicks on extension sources, it will automatically download & install the extension which will make the extension ui more interactive.

[kazemcodes]

Huge Thanks for your contribution