Add "Update approvals" page

• Add a new "updates" page with approvals and updates check.
• Make submenu for package management with the following structure:

• Package management
  • Packages
  • Updates (new page with approvals)
  • Settings (for updates)

• Add dropdown in top bar providing the following functionality:
• Add button for check updates to the "Updates" page.

It's better to solve this issue with #104 (closed) at the same time.