passStringToWasm0 is returning a pointer to our "arg" string in memory.
malloc - allocates or adds. realloc - reallocates or removes.
Unsigned right shift (>>>), https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Unsigned_right_shift, also called "zero filling right shift". (type of "bitwise shift", like ">>")
The Uint8Array typed array represents an array of 8-bit unsigned integers. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array