Project files download button functionality (FE)

[MariusJulius]

Figma (https://www.figma.com/file/VqCwED3Dymn7L1gGoAOK27/EKI-t%C3%B5lkev%C3%A4rav?type=design&node-id=1157%3A88211&mode=design&t=yUg6RYTkMH5Xpupj-1)

BE: #484

To-do:

• Functionality for download files added under project (button is there - lähtefailid, abifailid)

[superspartak]

Included in this PR: https://github.com/keeleinstituut/tv-web/pull/137

[plakitkelly]

Can't download abifailid - Teadmata viga: 404 Lähtefailid - OK

[plakitkelly]

It's OK