Add example of reading from stdin (#18)

Makefile

@@ -10,7 +10,8 @@ browser_examples := \
 
 node_examples := \
 	cat\
-	http-server
+	http-server\
+	read_stdin
 
 all_examples := $(browser_examples) $(node_examples)
 

read_stdin/README.md

@@ -0,0 +1,7 @@
+# Example reading from stdin
+
+```
+npm install
+npx gren make src/Main.gren
+node app
+```

read_stdin/gren.json

@@ -0,0 +1,17 @@
+{
+    "type": "application",
+    "platform": "node",
+    "source-directories": [
+        "src"
+    ],
+    "gren-version": "0.5.2",
+    "dependencies": {
+        "direct": {
+            "gren-lang/core": "6.0.0",
+            "gren-lang/node": "5.0.0"
+        },
+        "indirect": {
+            "gren-lang/url": "5.0.0"
+        }
+    }
+}

read_stdin/package.json

@@ -0,0 +1,6 @@
+{
+  "private": true,
+  "dependencies": {
+    "gren-lang": "^0.5.2"
+  }
+}

read_stdin/src/Main.gren

@@ -0,0 +1,22 @@
+module Main exposing (main)
+
+import Node
+import Stream
+import Node exposing (Environment)
+import Init
+import Task
+
+
+main : Node.SimpleProgram a
+main =
+    Node.defineSimpleProgram init
+
+
+init : Environment -> Init.Task (Cmd a)
+init env =
+    Stream.writeStringAsBytes "What is your name?\nName: " env.stdout
+        |> Task.andThen (\_ -> Stream.readBytesAsString env.stdin)
+        |> Task.map (Maybe.withDefault "") -- ignoring if we can't convert stdin bytes to string
+        |> Task.andThen (\name -> Stream.writeStringAsBytes ("Hi, " ++ name) env.stdout)
+        |> Task.onError (\_ -> Task.succeed env.stdout) -- ignoring all stream-related errors
+        |> Node.endSimpleProgram