Add Finnish string translations to the project

[juhalehtonen]

Description

This PR adds Finnish string translations to the project's i18n resources.

Impacted Areas in the application

This PR adds Finnish translations to the available i18n resources. Thanks to @ivan-aksamentov 's contribution, this PR also adds the Finnish language as a dropdown option in the language selector.

Testing

Testing should be done by changing the language to Finnish and viewing through all UI elements of the application.

[vercel[bot]]

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🔍 Inspect: https://vercel.com/neherlab/covid19-scenarios/9fs9iath4
✅ Preview: https://covid19-scenarios-git-625a9755fba6d4116b2134847b4a221c8e1c64dd.neherlab.vercel.app

[ivan-aksamentov]

@juhalehtonen Hi Juha,

Thanks so much for the contribution!

If you don't mind, I added Finnish language to the dropdown menu.

I unfortunately don't possess any Finnish language skills. If you have a minute, please verify that everything works as intended (you can use Vercel preview link above). And if it looks good, let me know and we will merge and release this.

P.S. Could you please also check that the number formatting on the plot and in tables is correct and looks natural for Finnish language? (we have a library that switches number formatting depending on language)

[juhalehtonen]

Hello @ivan-aksamentov !

Thank you so much for your input. I'm a bit busy this weekend, but I'll definitely check everything through and will update the PR accordingly.

There were a couple of strings still missing, and I still want to double-check that my use of terminology matches what I've seen in Finnish media and other outlets for consistency and clarity. Now that I had a look at the vercel app with your additions, the increased context allows me to see that I can tweak a couple of strings to feel more natural in their usage.

I'll also have a look at the number formatting as per your request :)

[juhalehtonen]

I've added and improved translations, and also verified that the number formatting makes sense for a Finnish user. I'm still not 100% happy with the texts, and will create at least one more commit before changing the PR draft status. Getting close though :)

As a sidenote: while verifying and testing my translations, I noticed that not every UI string seemed to be present on the english language base file (as in, not every string seemed to be translatable). I didn't see an existing issue about this, so perhaps I'm just missing something.

[juhalehtonen]

I've added some more missing translations and updated a few strings to better match the intended purpose and context. I changed the status of this PR from draft to ready, allowing it to be merged.

[ivan-aksamentov]

Thanks a lot @juhalehtonen ! Merging this.

Indeed, the i18next setup seems to be currently buggy. I created an issue for that: #808