spec: set html dir attribute in base config

test plan:
 * Verify Jenkins passes

Change-Id: I4a1cf9a2cb1e7941f4986a28c39ea816ca4b3626
Reviewed-on: https://gerrit.instructure.com/153237
Tested-by: Jenkins
Reviewed-by: Clay Diffrient <cdiffrient@instructure.com>
Product-Review: Jeremy Neander <jneander@instructure.com>
QA-Review: Jeremy Neander <jneander@instructure.com>

spec/javascripts/webpack_spec_index.js

@@ -19,6 +19,7 @@
 import { canvas } from '@instructure/ui-themes/lib'
 import './support/sinon/sinon-qunit-1.0.0'
 
+document.dir = 'ltr'
 const fixturesDiv = document.createElement('div')
 fixturesDiv.id = 'fixtures'
 document.body.appendChild(fixturesDiv)