Add C++ and mongoDB badge

[suveshmoza]

Please add badges for C++ and mongoDB.

[Bennyhwanggggg]

+1

[Railly]

I've already created a C++ badge. https://github.com/Railly/ColoredBadges

[Isaac-Tait]

@Railly Would you please provide a link to the C++ badge, I cannot find it. Thank you.

[Railly]

Sure, it's here: https://github.com/Railly/ColoredBadges/blob/master/svg/dev/languages/cpp.svg