Add concat.

lib/index.js

@@ -103,6 +103,26 @@ const Channel = function(length = 0) {
 
   const readOnly = Object.freeze(
     Object.assign(Object.create(prototype), {
+      concat: (...args) => {
+        const output = Channel();
+
+        (async () => {
+          await readOnly.forEach(output.push);
+
+          for (let index = 0; index < args.length; index++) {
+            const arg = args[index];
+
+            await (Channel.isChannel(arg)
+              ? arg.forEach(output.push)
+              : output.push(arg));
+          }
+
+          output.close();
+        })();
+
+        return output;
+      },
+
       every: async (callbackfn, thisArg) => {
         for (;;) {
           const value = await readOnly.shift();