Factor out copywriting to `en.json`

[chartgerink]

In order to prepare for localization, we need to factor out all text into the /langs/en.json file. This is a continuation of the work in #581.

In essence, we need to structure the /langs/en.json file with a lot of keys and strings that will be the text presented in English. For example:

{
  "translation": {
    "hero": "Step by step publishing of your research",
    "hero_subtitle": "A new publishing format: Research modules."
  }
}

Part of this issue is to find a good structure for the key and to ensure all the text that would need to be translated is in there. Please make sure to not forget checking all the non-visual aspects like aria-label and others!

We are starting to document the work for localization over in the Wiki - additional edits there are welcome as necessary while working on this.

Todo

• [ ] Add i18 to each page (import "../core/i18n")
• [ ] Add useTranslation to components (for the t method)
• [ ] Consistent naming scheme for text
• [ ] Actually factoring out the strings

[chartgerink]

Closing this as it's been open for a while and we're clearly not doing it at the moment. Will move to our backlog so we don't lose track.