test: replace karma with web-test-runner (#401)

* chore: add initial web-test-runner config

* refactor: distrubute custom element import statements (#395)

* refactor: distribute custom element imports

* test: import statements in unit and integratons tests

* fix: add missing import statements

Co-authored-by: Christian Dinkel <chhildeb@gmail.com>

* chore: remove karma config

* test: remove karma path definition to testfiles

* test: downgrade open-wc/testing and wtr to avoid lit2.0 collision

* test: await equalSnapshot

* chore: update package and package-lock

* chore: update package-lock after rebase

* test: remove karma base path

* test: add unit and integration test group

* test: add missing --group on script test

* chore(web-test-runner): run tests directly on *.ts files

* refactor: remove escapes from pattern string definition - conflit with wtr snapshot generation

* test: remove karma snapshots add wtr snapshots

* chore: update package-lock

* test: make zero-line unit test fail save

* chore: move snowpack config to snopack.config file

Co-authored-by: Jakob Vogelsang <jakob.vogelsang@omicronenergy.com>
Co-authored-by: Jakob Vogelsang <jakob-vogelsang@posteo.de>