Add Kelp cryptocurrency trading bot (#2420)

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- github.com repo: [https://github.com/stellar/kelp](https://github.com/stellar/kelp)
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README.md

@@ -163,6 +163,7 @@ Please take a quick gander at the [contribution guidelines](https://github.com/a
 * [Golang CryptoTrading Bot](https://github.com/saniales/golang-crypto-trading-bot) - A golang implementation of a console-based trading bot for cryptocurrency exchanges.
 * [govkbot](https://github.com/nikepan/govkbot) - Simple Go [VK](https://vk.com) bot library.
 * [hanu](https://github.com/sbstjn/hanu) - Framework for writing Slack bots.
+* [Kelp](https://github.com/stellar/kelp) - official trading and market-making bot for the [Stellar](https://www.stellar.org/) DEX. Works out-of-the-box, written in Golang, compatible with centralized exchanges and custom trading strategies.
 * [margelet](https://github.com/zhulik/margelet) - Framework for building Telegram bots.
 * [micha](https://github.com/onrik/micha) - Go Library for Telegram bot api.
 * [slacker](https://github.com/shomali11/slacker) - Easy to use framework to create Slack bots.