Add flattenthreads experiment

This experiment allows users to flatten the replies in threads, so they
are shown linearly in a chronological way instead of nested.

When the option is enabled, a switch is added to the thread page which
lets the user switch between flattening replies and not flattening them.

Some UI is still missing (see the design document[1]).

[1]: https://docs.google.com/document/d/1P-HanTHxaOFF_FHh0uSv0GIhG1dxWTJTGoT6VPjjvY0/edit

Bug: twpowertools:153
Change-Id: I43f94442cadc12b752700f0e8d974522be621d3e
diff --git a/webpack.config.js b/webpack.config.js
index 4f4a849..c515434 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -53,7 +53,7 @@
     batchLockInject: './src/injections/batchLock.js',
     xhrInterceptorInject: './src/injections/xhrProxy.js',
     extraInfoInject: './src/injections/extraInfo.js',
-    workflowComponentsInject: './src/injections/workflowComponentsInject.js',
+    litComponentsInject: './src/injections/litComponentsInject.js',
 
     // Options page
     optionsCommon: './src/options/optionsCommon.js',