Numeric separators break highlighting

[DanielRosenwasser]

const COULOMB = 8.957_551_787e9; // N-m^2 / C^2
const PLANCK  = 6.626_070_040e-34; // J-s
const JENNY   = 867_5309; // C-A-L^2
let bits = 0b1100_1100;
let routine = 0xC0FFEE_F00D_BED;