Update README

README.md

@@ -7,4 +7,42 @@
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-Work in progress.
+Command execution in Gulp.js.
+
+As opposed to
+[`child_process.exec()`](https://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback)
+or other plugins, `gulp-execa` uses the popular
+[`execa`](https://github.com/sindresorhus/execa) library:
+
+- [Better Windows support](https://github.com/IndigoUnited/node-cross-spawn#why),
+  including [shebangs](<https://en.wikipedia.org/wiki/Shebang_(Unix)>).
+- Faster and more secure, as it does not use a shell (by default).
+- Execution of locally installed binaries.
+- Descriptive errors and configurable verbosity.
+- Interleaved stdout/stderr.
+
+Commands can be executed either directly or inside a files stream. Unlike
+similar libraries, in streaming mode:
+
+- commands are run [in parallel](https://github.com/almost/through2-concurrent),
+  not [serially](https://github.com/rvagg/through2).
+- output can be saved either in files or in variables.
+
+Example Gulpfile:
+
+```js
+const { task, exec, stream } = require('gulp-execa')
+const { src, dest } = require('gulp')
+
+module.exports.audit = task('npm audit')
+
+module.exports.outdated = async function() {
+  await exec('npm outdated')
+}
+
+module.exports.sort = function() {
+  return src('**/*.txt')
+    .pipe(stream(({ path }) => `sort ${path}`))
+    .pipe(dest('sorted'))
+}
+```