Merge pull request #2157 from softwaremill/pekko-docs-v3

Add Pekko to supported backends

docs/backends/summary.md

@@ -8,6 +8,7 @@ Which one to choose?
 
 * for simple exploratory requests, use the [synchronous](synchronous.md) `HttpClientSyncBackend`.
 * if you have Akka in your stack, use the [Akka backend](akka.md)
+* if you have Pekko in your stack, use the [Pekko backend](pekko.md)
 * if you are using `Future` without Akka, use the `HttpClientFutureBackend`
 * finally, if you are using a functional effect wrapper, use one of the "functional" backends, for [ZIO](zio.md), [Monix](monix.md), [Scalaz](scalaz.md), [cats-effect](catseffect.md) or [fs2](fs2.md). 
 
@@ -30,6 +31,7 @@ Class                                Effect type                      Supported
 ``HttpURLConnectionBackend``         None (``Identity``)              n/a                                               no                         no
 ``TryHttpURLConnectionBackend``      ``scala.util.Try``               n/a                                               no                         no
 ``AkkaHttpBackend``                  ``scala.concurrent.Future``      ``akka.stream.scaladsl.Source[ByteString, Any]``  yes (regular & streaming)  yes
+``PekkoHttpBackend``                 ``scala.concurrent.Future``      ``org.apache.pekko.stream.scaladsl.Source[ByteString, Any]`` yes (regular & streaming)  yes
 ``ArmeriaFutureBackend``             ``scala.concurrent.Future``      n/a                                               no                         yes
 ``ArmeriaScalazBackend``             ``scalaz.concurrent.Task``       n/a                                               no                         yes
 ``ArmeriaZioBackend``                ``zio.Task``                     ``zio.stream.Stream[Throwable, Byte]``            no                         yes
@@ -94,4 +96,4 @@ Finally, there are third-party backends:
 
 * [sttp-play-ws](https://github.com/scalamania/sttp-play-ws) for "standard" play-ws (not standalone).
 * [akkaMonixSttpBackend](https://github.com/fullfacing/akkaMonixSttpBackend), an Akka-based backend, but using Monix's `Task` & `Observable`.
-* [be-kind-rewind](https://github.com/reibitto/be-kind-rewind), a VCR testing library for Scala
+* [be-kind-rewind](https://github.com/reibitto/be-kind-rewind), a VCR testing library for Scala