Add an option to show window from the taskbar

**Is your feature request related to a problem? Please describe.**
When IPFS desktop starts, the main window disappears and the icon exists on the taskbar. Since the window is hidden, there is no way to access the UI unless an option like `Preferences` or `Advanced` is selected.

**Describe the solution you'd like**
Have a simple `Show Window` button to display the UI. At least on mac, the use on other OSes is not clear.