Package maintenance

[gavinr]

Doing a bunch of maintenance chores, all of which fall under the category of "mirroring esri-leaflet." This should close all the dependabot PRs.

1. d57dacc - Updated all testing dependency versions to match esri-leaflet
2. db15187 - Switched from rollup-plugin-terser to @rollup/plugin-terser (Update dependencies esri-leaflet#1351)
3. be203d2 - Switch from karma-chai-sinon to karma-sinon-chai - Switch from karma-chai-sinon to karma-sinon-chai esri-leaflet#1335
   • Also updated our karma.conf.js settings. The "Reporter" changes change our testing reaporting from this:
     • 
     • to this:
     • 😍
4. 0e89880 - switched from watch to chokidar (switch from watch to chokidar esri-leaflet#1324)
5. 0e89880 - switched to npm-run-all (run-p) (Esri/esri-leaflet@09c18cb)
6. 8fb7c14 - removed travis and switched to github actions (Automated testing with GitHub actions esri-leaflet#1336)

[patrickarlt]

LGTM!