feat(nibijs): export string names of event types.

[Unique-Divine]

          (Not from your change, but I just noticed) We should import this string rather than hard-coding it here. That way, if we change the version of `@nibiruchain/nibijs` and `@nibiruchain/protojs`, we'll always have the correct type set here. 

For message types, we're able to import like this:

import { SPOT_MSG_TYPE_URLS } from "@nibiruchain/nibijs/dist/msg/spot"

// ... 
(e) => e.type === SPOT_MSG_TYPE_URLS.MsgJoinPool

For events, there's no equivalent. We should implement these exports in nibijs to make the emitted event types obvious.

Originally posted by @Unique-Divine in https://github.com/NibiruChain/web-app/pull/388#discussion_r1211931423