Add a Snowplow destinations

[alexanderkirtzel]

Is your feature request related to a problem? Please describe.
I want to implement Snowplow and send standard and custom events to it. I want to make use of my complete walker.js setup to add it easily.

Describe the solution you'd like
A Snowplow destination, please.

Describe alternatives you've considered
Use the Snowplow JavaScript tracker as a standalone library and maintain multiple data-collection setups.

Additional context
https://docs.snowplow.io/docs/collecting-data/collecting-from-own-applications/javascript-trackers/
https://github.com/snowplow/snowplow-javascript-tracker