PLT-5308 Caching layer part 2 (#6973)

* Adding Reaction store cache layer example

* Implementing reaction store in new caching system.

* Redis for reaction store

* Adding redis library

* Adding invalidation for DeleteAllWithEmojiName and other minor enhancements

vendor/github.com/go-redis/redis/doc.go

@@ -0,0 +1,4 @@
+/*
+Package redis implements a Redis client.
+*/
+package redis