Added SwiftDataLoader to 'Other implementations' (#149)

Author: kimdv

README.md

@@ -491,6 +491,8 @@ Looking to get started with a specific back-end? Try the [loaders in the example
   * [dataloader](https://github.com/absinthe-graphql/dataloader)
 * Golang
   * [Dataloader](https://github.com/nicksrandall/dataloader)
+* Swift
+  * [SwiftDataLoader](https://github.com/kimdv/SwiftDataLoader)
 * Rust
   * [Dataloader](https://github.com/cksac/dataloader-rs)
 * Perl