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Both shift instructions implementations are wrong

According to this documentations:
https://github.com/mattmikolay/chip-8/wiki/CHIP%E2%80%908-Instruction-Set
https://johnearnest.github.io/Octo/docs/chip8ref.pdf

The 8XY6 and 8XYE operations store the result of shifting the Vy register in Vx register.
Operating over Vx seems to be an incorrect descriptions of this operations behavior found in the S-CHIP original documentation. However this is not compatible with the original CHIP-8 implementation.

8js/src/CPU.js

Lines 516 to 542 in fb64163

/**
* 8xy6 - SHR Vx {, Vy}
*
* Set Vx = Vx SHR 1.
* If the least-significant bit of Vx is 1, then VF is set to 1, otherwise 0. Then Vx is divided by 2.
*
* @param reg
*/
CPU.prototype.shr = function shiftRigth(reg) {
this.reg.writeUInt8(this.reg[reg] & 0x1, 0xF);
this.reg.writeUInt8(this.reg[reg] >> 1, reg);
this.nextInstruction();
};
/**
* 8xyE - SHL Vx {, Vy}
*
* Set Vx = Vx SHL 1.
* If the most-significant bit of Vx is 1, then VF is set to 1, otherwise to 0. Then Vx is multiplied by 2.
*
* @param reg
*/
CPU.prototype.shl = function shiftLeft(reg) {
this.reg.writeUInt8(this.reg[reg] >> 7, 0xF);
this.reg.writeUInt8(this.reg[reg] << 1, reg, true);
this.nextInstruction();
};

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