Discord on Monday unveiled Nitro Rewards, which gives Nitro subscribers access to offers from other gaming and lifestyle brands for no additional cost.  Currently, Nitro offers upgrades to Discord itself, like more profile customization options, HD streaming, and the ability to upload files of up to 500 MB. The subscription is optional, as you can easily use the platform without paying, which is an intentional design choice on Discord’s part. But that also means user acquisition can be tricky. “Nitro has always been about how we can meaningfully upgrade the Discord experience, but not limit it [for free users] in any large way,” Stanislav Vishnevskiy, Discord’s co-founder and CTO, told TechCrunch. Nitro Rewards, available for both Nitro Basic ($2.99 per month) and Nitro ($9.99 per month) subscribers, is meant to improve the value for subscribers, and therefore retain them.…