Add Elixir SDK (stellar#12)

Author: juanhurtado10

docs/software-and-sdks/index.mdx

@@ -84,6 +84,12 @@ The Go SDK is split up into a few separate packages, all of which you can find i
 - [Docs](https://github.com/Soneso/stellar_flutter_sdk/tree/master/documentation)
 - [Examples](https://github.com/Soneso/stellar_flutter_sdk/tree/master/documentation/sdk_examples)
 
+### Elixir (beta)
+
+- [Source](https://github.com/kommitters/stellar_sdk)
+- [Docs](https://hexdocs.pm/stellar_sdk/readme.html)
+- [Examples](https://github.com/kommitters/stellar_sdk/blob/main/docs/examples.md)
+
 ## Tools
 
 The Stellar Development Foundation maintains a small suite of tools to make it easier for developers to interact with the network.