Match all files in public folder for sw.js (mui#187)

Currently, only first-level content of public folder will be included in sw.js, including folders. This way, only files, including nested ones, will be included. 

Also, don't use basename as it doesn't play nicely with deep files, instead use path.relative()

tools/webpack/configFactory.js

@@ -320,11 +320,11 @@ function webpackConfigFactory({ target, mode }, { json }) {
               const clientBundleAssets = globSync(
                 path.resolve(appRootPath, envVars.BUNDLE_OUTPUT_PATH, './client/*.js')
               );
-              return globSync(path.resolve(appRootPath, './public/*'))
+              return globSync(path.resolve(appRootPath, './public/**/*.*'))
                 .reduce((acc, cur) => {
                   // We will precache our public asset, with it being invalidated
                   // any time our client bundle assets change.
-                  acc[`/${path.basename(cur)}`] = clientBundleAssets; // eslint-disable-line no-param-reassign,max-len
+                  acc[`/${path.relative(path.resolve(appRootPath, 'public'), cur)}`] = clientBundleAssets; // eslint-disable-line no-param-reassign,max-len
                   return acc;
                 },
                 {