📝 Add documentation comments on root module

Author: lambdalisue

denops_std/mod.ts

@@ -1,3 +1,52 @@
+/**
+ * Standard module for [denops.vim](https://github.com/vim-denops/denops.vim).
+ *
+ * This module is assumed to be used for developing denops plugins. The code
+ * is assumed to be called in a dedicated worker thread of each plugins.
+ *
+ * By using this module, developers can write Vim/Neovim denops plugins like:
+ *
+ * ```typescript
+ * import { Denops } from "./mod.ts";
+ * import * as fn from "./function/mod.ts";
+ * import * as vars from "./variable/mod.ts";
+ * import * as helper from "./helper/mod.ts";
+ *
+ * import * as unknownutil from "https://deno.land/x/unknownutil/mod.ts";
+ *
+ * export async function main(denops: Denops): Promise<void> {
+ *   denops.dispatcher = {
+ *     async say(where: unknown): Promise<void> {
+ *       unknownutil.assertString(where);
+ *
+ *       const name = await fn.input(denops, "Your name: ");
+ *       const progname = await vars.v.get(denops, "progname");
+ *       const messages = [
+ *         `Hello ${where}.`,
+ *         `Your name is ${name}.`,
+ *         `This is ${progname}.`,
+ *       ];
+ *       await helper.echo(denops, messages.join("\n"));
+ *     },
+ *   };
+ *
+ *   await helper.execute(
+ *     denops,
+ *     `
+ *     command! HelloWorld call denops#notify("${denops.name}", "say", ["World"])
+ *     command! HelloDenops call denops#notify("${denops.name}", "say", ["Denops"])
+ *     `,
+ *   );
+ * }
+ * ```
+ *
+ * See [Denops Documentation](https://vim-denops.github.io/denops-documentation/)
+ * or [denops-helloworld.vim](https://github.com/vim-denops/denops-helloworld.vim)
+ * for more details.
+ *
+ * @module
+ */
+
 // Re-export
 export type {
   BatchError,