Add client-side custom filter support to glitch-soc

Port cdb101340a to glitch-soc,
but without dropping support for regexp filters yet.

app/javascript/flavours/glitch/reducers/index.js

@@ -27,6 +27,7 @@ import height_cache from './height_cache';
 import custom_emojis from './custom_emojis';
 import lists from './lists';
 import listEditor from './list_editor';
+import filters from './filters';
 
 const reducers = {
   dropdown_menu,
@@ -57,6 +58,7 @@ const reducers = {
   custom_emojis,
   lists,
   listEditor,
+  filters,
 };
 
 export default combineReducers(reducers);