src/vs/base/browser/ui/selectBox/selectBoxCustom.ts/SelectBoxList/onCharacter
class SelectBoxList:	private onCharacter(e: StandardKeyboardEvent): void {
		const ch = KeyCodeUtils.toString(e.keyCode);
		let optionIndex = -1;

		for (let i = 0; i < this.options.length - 1; i++) {
			optionIndex = (i + this.selected + 1) % this.options.length;
			if (this.options[optionIndex].text.charAt(0).toUpperCase() === ch && !this.options[optionIndex].isDisabled) {
				this.select(optionIndex);
				this.selectList.setFocus([optionIndex]);
				this.selectList.reveal(this.selectList.getFocus()[0]);
				dom.EventHelper.stop(e);
				break;
			}
		}
	}