Add web worker to browser testes

[hakanols]

When running time consuming testes in browser the entire page freeze. One solution to this is to run the testes in a web worker. Web workers calling es6 modules is support by chrome but not for Firefox at time of writing. Suggesting waiting for Firefox support before implementing.

Demonstrating problem:
https://hakanols.github.io/tweetnacl-es6/test/browser/test.html

Blocker:
https://bugzilla.mozilla.org/show_bug.cgi?id=1247687

[hakanols]

Firefox v111 will probably have Web Worker ES6 support. Have done some experimentation in:
https://hakanols.github.io/spel/Web_Worker/index.html