v3: Built in testrunner from Playwright and NodeJS

[eklem]

• Node built in testrunner - node-core-test
• Playwright built in testrunner
• Rollup
• What's needed for running files over http, to be able to test ESM-scripts imported. Maybe prebuild something to just plug in when needed?

[eklem]

Develop on branch v3

[eklem]

For running a mini webserver, maybe one of these:

• nginx
• express