Links to install prerequisites don't open in new tab.

See [here](https://keybase.io/docs/command_line/prerequisites).

Very minor issue, however it would be better to see the links to install the requirements open in a new tab/window rather than leave the documentation page.

Start with the linked prerequisites documentation at https://keybase.io/docs/command_line/prerequisites and inspect the links used to install requirements. Update the relevant documentation so those links open in a new tab or window, then verify that the documentation page remains open when each install link is followed.

Written by the indexing model from the issue text.