async progress(line) {
        const progressLength = line.getAttribute(`${this.pfx}-progressLength`)
            || this.progressLength;
        const progressChar = line.getAttribute(`${this.pfx}-progressChar`)
            || this.progressChar;
        const chars = progressChar.repeat(progressLength);
		const progressPercent = line.getAttribute(`${this.pfx}-progressPercent`)
			|| this.progressPercent;
        line.textContent = '';
        this.container.appendChild(line);

        for (let i = 1; i < chars.length + 1; i++) {
            await this._wait(this.typeDelay);
            const percent = Math.round(i / chars.length * 100);
            line.textContent = `${chars.slice(0, i)} ${percent}%`;
			if (percent>progressPercent) {
				break;
			}
        }
    }
Animate a progress bar.
@param {Node} line - The line element to render.