Add navbar tests, fix Jest/Babel configs

[gfrn]

• Add navbar tests
• Jest was declared as a module, but had no default export, this makes the Jest config a module. Babel has been made CommonJS, as it is the standard with this version of Babel

Next, I think I'll add workflow actions for automatically running unit tests, and possible move to Vitest!

[VictoriaBeilsten-Edmands]

Thanks for adding these tests and for the config updates.
As we've got rid of "type": "module" in package.json do we still need to change babel.config.js to babel.config.cjs?

[gfrn]

I based this off an older master branch, but I'll test it without type: module later tomorrow

[gfrn]

That should do it, but it's not wholly necessary - it still uses CJS module exports than proper export

[VictoriaBeilsten-Edmands]

Thanks.