talk about maxNumberOfFiles and allowedFileTypes affecting system file dialog

website/src/docs/uppy.md

@@ -15,10 +15,10 @@ const uppy = Uppy({
   autoProceed: true,
   debug: false,
   restrictions: {
-    maxFileSize: false,
-    maxNumberOfFiles: false,
-    minNumberOfFiles: false,
-    allowedFileTypes: false
+    maxFileSize: null,
+    maxNumberOfFiles: null,
+    minNumberOfFiles: null,
+    allowedFileTypes: null
   },
   meta: {},
   onBeforeFileAdded: (currentFile, files) => currentFile,
@@ -52,10 +52,15 @@ Optionally provide rules and conditions for which files can be selected.
 
 **Parameters**
 
-- `maxFileSize` *number*
-- `maxNumberOfFiles` *number*
-- `minNumberOfFiles` *number*
-- `allowedFileTypes` *array* of wildcards or exact mime types, like `image/*`
+- `maxFileSize` *null | number*
+- `maxNumberOfFiles` *null | number*
+- `minNumberOfFiles` *null | number*
+- `allowedFileTypes` *null | array* of wildcards `image/*`, exact mime types `image/jpeg`, or file extensions `.jpg`: `['image/*', '.jpg', '.jpeg', '.png', '.gif']`
+
+`maxNumberOfFiles` affects the number of files user is able to select via the system file dialog in UI plugins like `DragDrop`, `FileInput` and `Dashboard`: when set to `1` they will only be able to select a single file, otherwise, when `null` or other number, they will be able to select multiple files.
+
+`allowedFileTypes` array also gets passed to the system file dialog (see [`input[type=file]` accept](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input/file#Limiting_accepted_file_types)), so user will only be able to select images, for example.
+
 
 ### `meta: {}`