use md5 to hash webpack bundles

test plan:
* all eyes of the hot potato approve

Change-Id: Idaa349b2a5b526b46bfe72df2673093fb6ff88b3
Reviewed-on: https://gerrit.instructure.com/139120
Tested-by: Jenkins
Reviewed-by: Ryan Shaw <ryan@instructure.com>
QA-Review: Brent Burgoyne <bburgoyne@instructure.com>
Product-Review: Jeremy Neander <jneander@instructure.com>

frontend_build/baseWebpackConfig.js

@@ -26,6 +26,7 @@ const bundleEntries = require('./bundles')
 const BundleExtensionsPlugin = require('./BundleExtensionsPlugin')
 const ClientAppsPlugin = require('./clientAppPlugin')
 const CompiledReferencePlugin = require('./CompiledReferencePlugin')
+const HashOutput = require('webpack-plugin-hash-output')
 const I18nPlugin = require('./i18nPlugin')
 const SelinimumManifestPlugin = require('./SelinimumManifestPlugin')
 const WebpackHooks = require('./webpackHooks')
@@ -83,6 +84,8 @@ module.exports = {
   }, bundleEntries, momentLocaleBundles),
 
   output: {
+    hashDigestLength: 10,
+
     path: path.join(__dirname, '../public', webpackPublicPath),
 
     // Add /* filename */ comments to generated require()s in the output.
@@ -272,6 +275,7 @@ module.exports = {
     // be removed when that issue is fixed
     new webpack.IgnorePlugin(/\.flow$/),
 
+    new HashOutput()
   ]
   .concat(process.env.SELINIMUM_RUN || process.env.SELINIMUM_CAPTURE ? [
 

package.json

@@ -146,6 +146,7 @@
     "webpack-cleanup-plugin": "^0.5.1",
     "webpack-manifest-plugin": "^1.3.2",
     "webpack-parallel-uglify-plugin": "^1.0.0",
+    "webpack-plugin-hash-output": "^1.3.0",
     "xsslint": "0.1.4",
     "yaml-loader": "^0.5.0"
   },

yarn.lock

@@ -11311,6 +11311,10 @@ webpack-parallel-uglify-plugin@^1.0.0:
     webpack-sources "^1.0.0"
     worker-farm "^1.3.1"
 
+webpack-plugin-hash-output@^1.3.0:
+  version "1.3.0"
+  resolved "https://registry.yarnpkg.com/webpack-plugin-hash-output/-/webpack-plugin-hash-output-1.3.0.tgz#998eb655bc2216fca95608735645f9c752532ce6"
+
 webpack-sources@^1.0.0, webpack-sources@^1.0.1:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/webpack-sources/-/webpack-sources-1.1.0.tgz#a101ebae59d6507354d71d8013950a3a8b7a5a54"