Bugfix and some improvements for 0.1.1

I made a lot of changes and fixed one of two bugs that were noticed. Which is double jump not working.

I did some balance changes and removed platform speed upgrade from shop as it was kind of a trap. It made not do some jumps you would do.

I added Credits scene because well. I do use some assets that I didn't make.

I also added submenu for first game and some guide on how to play it (if it wasn't obvious but just in case.)

I also made a discord server for updates

https://discord.gg/zE4EgPjUdX