Add dark mode

[Uziniii]

No description provided.

[angeluriot]

Thanks! But there are some issues:

• Home
  • The white of the background and that of the buttons is not the same to distinguish them better. In dark mode, both are the same black, so it is very difficult to see the buttons
  • The background points are not part of the transition, they instantly turn black
  • I think the button would be better on the top right of the page, there is already a lot of buttons here, especially on mobile
  • The button is not responsive, it goes wrong as soon as you change the window size
• Maps
  • In dark mode, the background black and buttons black are the same black
  • No transition here, everything changes instantly
  • The hover shadow on map groups and maps doesn't work in dark mode
  • The small triangles stay black in dark mode
  • The "All maps" emoji is gone (even in white mode)
  • In white mode the two existing buttons have the wrong white
  • I think the button would be better on the right
  • The button is not responsive, it goes wrong as soon as you change the window size
• Statistics
  • In dark mode, the background black and buttons black are the same black
  • No transition here, everything changes instantly
  • The "Statistics" emoji is gone (even in white mode)
  • In white mode the two existing buttons have the wrong white
  • I think the button would be better on the right
  • The button is not responsive, it goes wrong as soon as you change the window size
  • The graph backgrounds are always dark and the rest of the graphs are always in white mode
• Map
  • In dark mode, the background black and buttons black are the same black
  • No transition here, everything changes instantly
  • In white mode the existing button have the wrong white and is smaller
  • The title is gray in both modes
  • The bottom right buttons are always in white mode
  • The button is not responsive, it goes wrong as soon as you change the window size
  • I think the button would be better on the top right of the page

To be honest, a dark mode that works well is not that easy to do, maybe you can leave it like that and I'll start from your PR to do it myself when I have time