[#507] feat: add frontend test github workflow

[MSzalowski]

Set up test_frontend workflow to dispatch automated tests on every pull request.

List of changes

• add frontend test github workflow that executes test script in govtool/frontend package.

Checklist

• related issue
• My changes generate no new warnings
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the changelog
• I have added tests that prove my fix is effective or that my feature works

[placek]

Apart from a minor typo, looks solid. Good job so far!

[placek]

LGTM 👍