I actually thought about this too, but the problem is that in order to implemented effectively it would need to pull from an external data source, maybe a google doc spreadsheet or something. From what I've seen, people start getting VERY suspicious of chrome extensions when they start pulling data in from other sites.
I could build a small database file and include it with the extension, but it would only be updated when the extension itself updated, which takes out the crowd-sourcing component.
I've thought about doing a similar system for games that have 3rd party (non-Steam) DRM.
Yeah the unannounced surprise 3rd party DRM, or even just having it buried in the fine print, its extremely obnoxious. I really hate that I have to spend a lot of time investigating if games have it or not, but I have come to have certain publishers on my crappy 3rd party DRM shit list (Focus, Ubi etc).
Still, I have gotten surprised by the 3rd party DRM in the past and it really pissed me the hell off. That's the kind of thing I want to know before I buy.
I get what you are saying though. It'd be nice to have the community update these things but it gets complicated. I know there is that Big List of 3rd Party DRM on Steam that flibitijibibo maintains which I am infinitely thankful for.
I don't really know if there's a good way to pluginize that or the DLC issue. I guess you could have a button for people to submit it and then add it based on that, but you'd be taking their word and it's open to abuse and misinformation.