Introducing unit tests basis

Background / User story

Currently we do not have unit tests implemented, we have smoke tests, linters. This ticket is for unit tests basis introduction.

What to change

• Introduce unit tests basis (@ThomasGreiner already started this here)
• Create test one for each type of script file below:
  • Various Libraries/APIs(lib folder, drawing-handler.js, DOM.js and etc.)
  • Components(io-list-box, io-filter-table and etc.)
  • Build tools(font-generations, csv-exporter)

Further information

New adblockplusui tests will be introduced that will be run on npm test or npm run test.