Commuter bike options for my 4.5 mile commute

I just got a new job and my office is so close to my house that I'd like to save on gas (and my health!) and invest in a commuter bike. 90% of my bike commute would be on paved community trails, and the last mile or so would be sharing a stretch of road with vehicles. What bike style should I consider purchasing?

I am totally new to this concept, so if anyone has any expertise, or a subreddit I can direct this question to, please let me know, thanks you!