Add flint & steel to /shop (for QoL)

There are two main uses for flint & steel - lighting nether portals, and lighting TNT. If you want flint & steel, you can buy iron ($24), and gravel ($3), but then you have to mine the gravel until it randomly drops flint. I think it would be nice if you could buy flint & steel (or at least flint) from the shop and not have to deal with the random gravel drops. Only thing to consider - this could affect SOTW (as it may or may not be faster to reach corners by going nether) assuming nether is enabled at SOTW. I am personally fine with this, especially if it removes an element of luck (flint drop), but unsure if others have opinions for/against this.