I'm sure most of us have referred to (and probably cited) caniuse.com at some point. It's probably the most comprehensive collection of browser feature support around. Want to know the status of CORS support? Here you go.
Well, now if you spot an error or want to add further information, you can do so fairly directly: caniuse.com is now on GitHub.
I should probably note that caniuse.com is monetized (in a very minimal, unobtrusive fashion at present), and perhaps you don't want to contribute to someone else's monetized project on the theory that, well, they're getting paid for this (assuming the ads cover the hosting). Fair enough. For me, barring big changes to the site, I'd be happy to add to the data there if I happen to know something that's not covered. It's a great resource, well-managed.
(Side note: I'm not affiliated with caniuse.com in any way, something that may not be obvious from the above.)