Added creative mode tab and sample block

That was actually harder than i thought, data generation would stop working, then i realized that i made the datagen class in main while it should be in client. This mistake cost me about an hour of troubleshooting.

I followed fabric’s docs, and i made the creative mode tab and the sample block, dk how to make a block entity for now but still learning as i really wanna complete this mod.

I also made the tab icon in aseprite, actually very easy and fun to use!

Devlog Recap:

- Made creative mode tab

- Added sample block, to be made into a real rain sensor in the future

- Set up datagen after struggling with it