Update frontend build system to shed old dependencies, and address fallout from that (#521)

* get tests working and update copyright headers

* lint fix

* eslint ts update

* update CI to use NPM

* fix CI

* prettier

* npm, not yarn for docker

* remove unused package

* bump dockerfile to latest node LTS and no need for cache clean

* make frontend Dockerfile work and remove unused SUBSTRATE_TELEMETRY_SAMPLE

* remove final yarn references

* add another comment

* remove unused import

* remove more unused deps

* comment typo

frontend/scripts/env.sh

@@ -12,7 +12,6 @@ echo -n > $TARGET
 
 declare -a vars=(
   "SUBSTRATE_TELEMETRY_URL"
-  "SUBSTRATE_TELEMETRY_SAMPLE"
 )
 
 echo "window.process_env = {" >> $TARGET