Document dot option (#148)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

readme.md

@@ -96,6 +96,34 @@ const deletedPaths = await deleteAsync(['temp/*.js'], {dryRun: true});
 console.log('Files and directories that would be deleted:\n', deletedPaths.join('\n'));
 ```
 
+##### dot
+
+Type: `boolean`\
+Default: `false`
+
+Allow patterns to match files/folders that start with a period (`.`).
+
+This option is passed through to [`fast-glob`](https://github.com/mrmlnc/fast-glob#dot).
+
+Note that an explicit dot in a portion of the pattern will always match dot files.
+
+**Example**
+
+```
+directory/
+├── .editorconfig
+└── package.json
+```
+
+```js
+import {deleteSync} from 'del';
+
+deleteSync('*', {dot: false});
+//=> ['package.json']
+deleteSync('*', {dot: true});
+//=> ['.editorconfig', 'package.json']
+```
+
 ##### concurrency
 
 Type: `number`\