feature(lang): Implement our own i18n system

[tougrel]

The way I'm thinking it is having a JSON file like this:

{
    "en-us": {
        "title": "Pestoverse",
        "nav.menu": "Menu",
        "nav.theme": "Theme"
    }
}

This should be easy enough to load into a Map and use it on the code like lang.get("title"); to get the result we want. It should also make the switch between languages easy and fast because we will be loading all strings at once instead of having to reload the page.

If anyone thinks that this will slow down the website loading then we can go with the second option of requesting the strings and adding them on the map via an API and only load the selected language by default! 👍