add support for sender_action (Typing indicator)
add support for sender_action (Typing indicator)

howdyai/botkit,ouadie-lahdioui/botkit,dhulser/slack-reporting-bot,DJ1K1/botkit,healthchatnow/hcn,howdyai/botkit,EliKrumholz/botkit,DJ1K1/botkit,howdyai/botkit,howdyai/botkit,acrollet/botkit,samuelsan/YelpBot