add small doc for jsx --completion

complete/README.md

@@ -0,0 +1,42 @@
+# JSX completion
+
+The JSX compiler has the completion mode for text editors / IDEs,
+triggered by `jsx --complete`.
+
+# CAVEAT
+
+This feature is alpha quality. Project to change.
+
+# USAGE
+
+`jsx --complete 15:7 complete/example.jsx` will shows the following JSON array:
+
+```json
+[
+   {
+      "word" : "window",
+      "definedFilename" : "/path/to/jsx/lib/js/js/web.jsx",
+      "definedClass" : "dom",
+      "doc" : "The top-level Window object.",
+      "type" : "Window",
+      "definedLineNumber" : 18
+   },
+   {
+      "args" : [
+         {
+            "name" : "id",
+            "type" : "string"
+         }
+      ],
+      "word" : "getElementById",
+      "definedClass" : "dom",
+      "definedFilename" : "/path/to/jsx/lib/js/js/web.jsx",
+      "type" : "function (: string) : HTMLElement",
+      "doc" : "same as <code>dom.document.getElement(id)</code>, except returns <code>HTMLElement</code>.",
+      "returnType" : "HTMLElement",
+      "definedLineNumber" : 35
+   }
+]
+```
+
+[jsx.vim](https://github.com/jsx/jsx.vim/blob/master/autoload/jsx.vim) uses this feature.

complete/example.jsx

@@ -0,0 +1,17 @@
+// usage: jsx --complete 15:7 complete/example.jsx
+
+import "js/web.jsx";
+
+/**
+ * The application main class.
+ */
+class _Main {
+	/**
+	 * The application entry point.
+	 * @param args arguments of process
+	 */
+	static function main(args : string[]) :void {
+		log "Hello, world!";
+		dom.
+	}
+}