Add support for 8.1.218 runner (from GM4HTML5 1.0.218)

[cher-nov]

As it turned out (https://github.com/cher-nov/gm8_compat/issues/2#issuecomment-828676518), 218 is almost nearly identical to 141, but also features some useful math functions and full support for 820 gmk format comparing to 141 (not only in game settings block but also in room and object ones).