Adding burns in the UI!

I changed several things in this devlog (well really only about two).
The first one is the time system. Now, under the slider, you can see the
time before or after “now.” The time in the future is predicted up to 8
hours ahead for selection of when to put the next burn. You can only
simulate burns in the future.

The other change is that now you can add a burn to the current point
selected in the future using an interface in the top right (early
prototype, the ui will be different later). You type in the number of
seconds the burn should last, move the time with the slider on the
bottom to when you want it to start. Then you press “start burn.” It
takes a second and I haven’t added a loading indicator there yet, but
does do things once you click it!

If you’d like to try these new changes out, go to the live demo on
https://burn.jmeow.net!

Note: I am aware that you can go right through Earth and it looks weird.
In the next devlog I’ll probably add an explosion when you hit Earth so
this doesn’t happen.

TL;DR: You can now add burns in-game and it simulates the trajectory of
the spacecraft 8 hours ahead.