For some pointers on the Godot side, I would take a look at the project settings under “General > Display > Window > Stretch > Mode” (see the docs for this settings as well). This changes how your game scales as the window is resized from it’s standard resolution. It defaults to “disabled”, but using “canvas_items” or “viewport” will scale up the game to match the window size (docs describe the difference, but I usually like to try both to see which one fits better for the game I am working on).
There’s also a nice article specifically on supporting multiple resolutions if you want to learn even more!
All this said, for a 7-day game jam I think it’s fine not to worry too much about this kind of thing. Better to spend the time focusing on the gameplay, art, etc. which you did very well on :D