Updated README to document new extra-args option (#8)

* Updated README to document new `extra-args` option

* Update README.md

Applying suggestions

Co-authored-by: Felix Fontein <[email protected]>

---------

Co-authored-by: Felix Fontein <[email protected]>

Author: x1101

README.md

@@ -64,6 +64,18 @@ The follow options can be provided to this GitHub Action.
       Example: <code>formatters codeqa</code>.
     </td>
   </tr>
+  <tr>
+    <td>
+      <code>extra-args</code>
+      <br>
+      (default:&nbsp;<code>""</code>)
+    </td>
+    <td>
+      Extra arguments to be passed to nox sessions. If empty, no extra arguments are passed. Can be a space-separated list of arguments.
+      <br>
+      Example: <code>--check</code>.
+    </td>
+  </tr>
   <tr>
     <td>
       <code>force-pythons</code>