Just Flax

Adds Flax, which can be planted and turned into string.
Flax seeds can be gathered from breaking grass.
Flax obtained the crop can be crafted into string in a 1:1 ratio.

As it may be noticeable to some, the textures look like ass because I am not a pixel artist.
If anyone wants to contribute to the mod by making better looking textures, I would greatly appreciate it.