Snowplow JavaScript Tracker v2.16.0

This release has seen many improvements to the build process as we continue on our journey to version 3 of the tracker.

v2.15.0 came in in 111KB (34KB when gzipped). The new v2.16.0 is a much improved 77KB (27KB when gzipped). This is ~30% smaller (or ~20% when gzipped) with the exact same functionality.

We've achieved this by switching to rollup.js and the closure compiler.

Build Improvements

Use Closure Compiler to reduce sp.js size (#583)
Switch to rollup and gulp (#752)

Under the hood

Switch to Github Actions (#844)
Add license banner to rollup builds (#845)
Bump snowplow-tracker-core to 0.9.2 (#841)
Update Snowplow Micro to v1 (#837)