Setting welcome banner topic

Discourse allows us to customize a banner for newcomers to the site. Once they ‘x’ out of it, they won’t see it again. Currently, I’ve copied over the text from our Google Group page, but I think it can still be improved. I propose adding a photo, some styling, and clear instructions for how to log in (for this we need to wait to figure out SSO).

For context:

Note: once you clear it, you can always see it again by opening up in an incognito window.