Don't require input attribute on <file-attachment>

Author: koddsson

README.md

@@ -15,15 +15,15 @@ import '@github/file-attachment-element'
 ```
 
 ```html
-<file-attachment directory input="upload">
-  <input id="upload" type="file" multiple>
+<file-attachment directory>
+  <input type="file" multiple />
 </file-attachment>
 ```
 
 ### Optional attributes
 
 - `file-attachment[directory]` enables traversing directories.
-- `file-attachment[input]` points to the ID of a file input inside of `<file-attachment>`. Files selected from the `<input>` will be attached to `<file-attachment>`. Supplying an input is strongly recommended in order to ensure users can upload files without a mouse or knowing where to paste files.
+- `file-attachment[input]` points to the ID of a file input inside of `<file-attachment>`. If supplied, only files selected from the corresponding `<input>` will be attached to `<file-attachment>`.
 
 ### Styling drag state
 

test/test.js

@@ -61,8 +61,8 @@ describe('file-attachment', function () {
     let fileAttachment, input
     beforeEach(function () {
       document.body.innerHTML = `
-        <file-attachment input="upload">
-          <input type="file" id="upload">
+        <file-attachment>
+          <input type="file">
         </file-attachment>`
 
       fileAttachment = document.querySelector('file-attachment')