[wip] Style on-hand button

Had to update the form controller a little bit to handle buttons.

But arrow not showwing on focus.
Getting some weird SCSS behaviour here.. maybe I'm trying to be too clever.

spec/javascripts/stimulus/bulk_form_controller_test.js

@@ -36,6 +36,7 @@ describe("BulkFormController", () => {
           <div data-record-id="1">
             <input id="input1a" type="text" value="initial1a">
             <input id="input1b" type="text" value="initial1b">
+            <button>a button is an element, but never changed</button>
           </div>
           <div data-record-id="2">
             <input id="input2" type="text" value="initial2">