Add special case for some plugin specs to webpack

For some reason some plugins like analytics have specs that
live in `spec_canvas/coffeescripts` it seems that webpack never
properly picked those up and complained about it in warnings.

Test Plan:
  - Webpack tests pass

Change-Id: I1c84f6850aa0501a5659aabde7768257e97a9253
Reviewed-on: https://gerrit.instructure.com/78723
Reviewed-by: Ryan Shaw <ryan@instructure.com>
Tested-by: Jenkins
Product-Review: Clay Diffrient <cdiffrient@instructure.com>
QA-Review: Clay Diffrient <cdiffrient@instructure.com>

frontend_build/baseWebpackConfig.js

@@ -95,7 +95,8 @@ module.exports = {
         include: [
           path.resolve(__dirname, "../app/coffeescript"),
           path.resolve(__dirname, "../spec/coffeescripts"),
-          /gems\/plugins\/.*\/app\/coffeescripts\//
+          /gems\/plugins\/.*\/app\/coffeescripts\//,
+          /gems\/plugins\/.*\/spec_canvas\/coffeescripts\//
         ],
         loaders: [
           "coffee-loader",

webpack.test.config.babel.js

@@ -42,6 +42,14 @@ testWebpackConfig.module.loaders.push({
   loaders: ["qunitDependencyLoader"]
 });
 
+// Some plugins use a special spec_canvas path for their specs
+testWebpackConfig.module.loaders.push({
+  test: /\/spec_canvas\/coffeescripts\//,
+  loaders: [
+    'qunitDependencyLoader'
+  ]
+});
+
 testWebpackConfig.module.loaders.push({
   test: /\/spec\/javascripts\/jsx\//,
   loaders: ["qunitJsxDependencyLoader"]