Set Hyperlinks to Open In New Tab/Window

[simonkurtz-MSFT]

Most, if not all, of the hyperlinks presently replace the current tab/window when executed. As we want to remain on the workshop page, we should open hyperlinks in new tabs/windows.

[simonkurtz-MSFT]

I was hopeful we could address this with config, but this is just for the auxiliary links.

I added a key to _config.yml called aux_links_new_tab, and if it's set to true, aux links will open in a new tab via target="_blank"

just-the-docs/just-the-docs#229