ci: add e2e tests with cypress

* Creates E2E tests using Cypress and includes two tests

* Improves yarn.lock file

* Includes documentation

* Cypress project id

* test e2e w/ ci and video

* run unit command before e2e

* Also cache cypress

* Persist cypress to next build step

* Try a different path

* Try without working dir

* Persist less data, but restore yarn/cypress cache in next step

* Install cypress to invalidate cache

* Add e2e as a blocker for merged publishing

.gitignore

@@ -25,3 +25,6 @@ yarn-error.log
 sampledata/
 example/deps/
 docker/dcm4che/dcm4che-arc
+
+# Cypress test results
+cypress/videos/