Improves documentation, and adding DocC (#6784)

Finished documenting flatbuffersbuilder

Replaces swift 5.5 with 5.2 packages

Starts building the tutorial for xcode 13

Finishes building the tutorial for xcode 13

Removes docc files from old swift versions

Updates swift style guide

grpc/examples/swift/Greeter/Sources/client/main.swift

@@ -37,7 +37,8 @@ func greet(name: String, client greeter: models_GreeterServiceClient) {
   builder.finish(offset: root)
 
   // Make the RPC call to the server.
-  let sayHello = greeter.SayHello(Message<models_HelloRequest>(builder: &builder))
+  let sayHello = greeter
+    .SayHello(Message<models_HelloRequest>(builder: &builder))
 
   // wait() on the response to stop the program from exiting before the response is received.
   do {
@@ -54,7 +55,8 @@ func greet(name: String, client greeter: models_GreeterServiceClient) {
   builder.finish(offset: manyRoot)
 
   let call = greeter.SayManyHellos(Message(builder: &builder)) { message in
-    print("Greeter SayManyHellos received: \(message.object.message  ?? "Unknown")")
+    print(
+      "Greeter SayManyHellos received: \(message.object.message  ?? "Unknown")")
   }
 
   let status = try! call.status.recover { _ in .processingError }.wait()

grpc/examples/swift/Greeter/Sources/server/main.swift

@@ -32,7 +32,8 @@ class Greeter: models_GreeterProvider {
 
   func SayHello(
     request: Message<models_HelloRequest>,
-    context: StatusOnlyCallContext) -> EventLoopFuture<Message<models_HelloReply>>
+    context: StatusOnlyCallContext)
+    -> EventLoopFuture<Message<models_HelloReply>>
   {
     let recipient = request.object.name ?? "Stranger"
 
@@ -40,17 +41,22 @@ class Greeter: models_GreeterProvider {
     let off = builder.create(string: "Hello \(recipient)")
     let root = models_HelloReply.createHelloReply(&builder, messageOffset: off)
     builder.finish(offset: root)
-    return context.eventLoop.makeSucceededFuture(Message<models_HelloReply>(builder: &builder))
+    return context.eventLoop
+      .makeSucceededFuture(Message<models_HelloReply>(builder: &builder))
   }
 
   func SayManyHellos(
     request: Message<models_HelloRequest>,
-    context: StreamingResponseCallContext<Message<models_HelloReply>>) -> EventLoopFuture<GRPCStatus>
+    context: StreamingResponseCallContext<Message<models_HelloReply>>)
+    -> EventLoopFuture<GRPCStatus>
   {
     for name in greetings {
       var builder = FlatBufferBuilder()
-      let off = builder.create(string: "\(name) \(request.object.name ?? "Unknown")")
-      let root = models_HelloReply.createHelloReply(&builder, messageOffset: off)
+      let off = builder
+        .create(string: "\(name) \(request.object.name ?? "Unknown")")
+      let root = models_HelloReply.createHelloReply(
+        &builder,
+        messageOffset: off)
       builder.finish(offset: root)
       _ = context.sendResponse(Message<models_HelloReply>(builder: &builder))
     }