build: Switch to webpack 5.

This has many fewer stale npm packages (so many fewer warnings).  Tests
can use all of modern javascript.  This should be easier to maintain in
the future.

Note the built bundles are somewhat smaller due to modernization of some
packages.

This is part of and closes #1132.

examples/blog-lines/index.pug

@@ -238,7 +238,7 @@ block append mainContent
           p A modest number of line segments from a real-world sample.
   #lines_list
     b Compare line drawing between libraries, versions, and rendering methods
-    div
+    #feature-div
       label(for='feature') Feature
       select#feature
     #info

examples/blog-lines/main.css

@@ -52,3 +52,6 @@ table tr>td:first-child {
   width: 322px;
   height: 24px;
 }
+#feature-div {
+  height: 27px;
+}

karma-base.js

@@ -222,9 +222,10 @@ var FirefoxPrefs = {
   'media.gmp-manager.url': ''
 };
 
-module.exports = function (config) {
-  webpack_config.plugins.push(function () {
-    this.plugin('done', function (stats) {
+/* If webpack of a test fails, stop rather than run some tests */
+class KarmaWarningsToErrorsWebpackPlugin {
+  apply(compiler) {
+    compiler.hooks.done.tap('KarmaWarningsToErrorsWebpackPlugin', (stats) => {
       if (stats.compilation.warnings.length) {
         // Log each of the warnings
         stats.compilation.warnings.forEach(function (warning) {
@@ -240,7 +241,12 @@ module.exports = function (config) {
         }];
       }
     });
-  });
+  }
+}
+
+module.exports = function (config) {
+  /* If webpack of a test fails, stop rather than run some tests */
+  webpack_config.plugins.push(new KarmaWarningsToErrorsWebpackPlugin());
   var newConfig = {
     autoWatch: false,
     files: [
@@ -312,12 +318,16 @@ module.exports = function (config) {
         }, FirefoxPrefs)
       }
     },
+    browserDisconnectTimeout: 30000,
+    browserDisconnectTolerance: 3,
     browserNoActivityTimeout: 300000,
     reporters: [
       'spec',  // we had used the 'progress' reporter in the past.
       'kjhtml'
     ],
-    // We could suppress passing results
+    /* enable for testing */
+    // logLevel: config.LOG_DEBUG,
+    /* We could suppress passing results */
     // specReporter = {suppressPassed: true, suppressSkipped: true},
     middleware: [
       'testimage',
@@ -330,7 +340,7 @@ module.exports = function (config) {
     ],
     preprocessors: {},
     frameworks: [
-      'jasmine', 'sinon'
+      'jasmine', 'sinon', 'webpack'
     ],
     client: {
       jasmine: {
@@ -339,9 +349,7 @@ module.exports = function (config) {
       }
     },
     webpack: {
-      /* webpack 4
-      mode: 'production',
-       */
+      mode: 'development',
       performance: {hints: false},
       cache: true,
       devtool: 'inline-source-map',