feat: basic Express backend server

[martakam]

This is a small PR which adds the backend server running Express for our application.
The next natural step would be adding GraphQL, since we will not be using classic REST.
After that, we must also add a database to store our data.

All of this will be added in separate PRs which build upon this one, so the backend is in no way complete yet.

[johahor]

Good work on the initial setup! A couple of things that should be fixed before merge.

.gitignore will stop working with this setup, and I see that you have fixed this in #23 on commit af09012, but it should added to this PR in case we merge this into main, and #23 takes some time to get merged as well. If you plan to merge them together, it's fine to leave as is. l

The README.md file references stale paths, some examples app/test, app/api, app/api/types.ts. I will also comment specifically on these lines in another review comment, so treat this as a general comment for it.

"Hello world!" works in localhost:3001, good good.

[johahor]

Good work on the initial setup! A couple of things that should be fixed before merge.

.gitignore will stop working with this setup, and I see that you have fixed this in #23 on commit af09012, but it should added to this PR in case we merge this into main, and #23 takes some time to get merged as well. If you plan to merge them together, it's fine to leave as is. l

The README.md file references stale paths, some examples app/test, app/api, app/api/types.ts. I will also comment specifically on these lines in another review comment, so treat this as a general comment for it.

"Hello world!" works in localhost:3001, good good.

It might be better to just merge PR 22-24 in one go (you might have already planned to do this), and approve this right away as is. I see you made some changes to documentation in #24, and it is probably better to make all documentation changes in that one, to avoid having to rebase the stacked PR's with this one.

Tell me what you think, and I'll approve if you agree.

[martakam]

Yes, these PRs should likely be merged together. Any issues that are more relevant in the next PRs can be resolved there