chore: upgrade dependencies

Upgrades all dependencies that can be upgraded. Major changes are:

• Removed fontawesome and used the raw svg directly instead. We only used 2 icons anyways.
• Upgraded reat-router. This had a few breaking changes so a few code edits were necessary.
• Migrated from bootstrap 4 to 5. A lot of little changes here and there, but most importantly the Jumbotron component does not exist anymore. I recreated one following the example in https://getbootstrap.com/docs/5.3/examples/jumbotron/. I did not bother making a 1:1 copy of the old design as we will probably rework everything anyways. (see #47 (closed))
• Upgraded from prettier 2 to 3. Major update to a few changes needed fixing.
• Simplified the eslint config. Reused the config from https://forge.extranet.logilab.fr/cubicweb/cubicwebjs/ as it is a lot simpler but at the same time catches a lot more errors. This also links prettier with eslint so running eslint --fix also fixes prettier. This is very useful when you configure your editor to run eslint --fix on save. I fixed a few errors but the few which needed more work were simply ignored for now.

Bootstrap 4	Bootstrap 5

Fixes #49 (closed)