How can I set the width of cells in a table using the docx library for Node.js?

I’m generating a .docx file using Node.js. In my header, I have a table that contains one row and two cells. The table spans the full width, and I’m trying to set the width of the cells as follows:

• The left cell, which contains an image, should be as wide as the
  image.
• The right cell, which contains text, should take up the remaining
  width of the row (100% of the row width minus the width of the
  image).

As per the documentation, I’m using the width property to define both the table’s width and the individual cell widths, but I can’t get it to work.
I also tried setting, as in the following example, the total table width to 100% and the two cells to 20% and 80%, respectively, but they still remain 50% wide each.

const headerImage = new ImageRun({
    type: 'png',
    data: fs.readFileSync("./public/assets/images/test-image.png"),
    transformation: {
        width: 120,
        height: 120,
    },
});

const heading = new Table({
    width: {
        size: 100,
        type: WidthType.PERCENTAGE,
    },
    rows: [
        new TableRow({
            children: [
                new TableCell({
                    width: {
                        size: 20,
                        type: WidthType.PERCENTAGE
                    },
                    verticalAlign: "center",
                    children: [
                        new Paragraph({
                            children: [
                                headerImage
                            ]
                        })
                    ],
                }),
                new TableCell({
                    width: {
                        size: 80,
                        type: WidthType.PERCENTAGE
                    },
                    verticalAlign: "center",
                    children: [
                        new Paragraph({
                            alignment: "center",
                            children: [
                                new TextRun({
                                    text: "Text1",
                                    bold: true,
                                    size: "30pt",
                                }),
                                new TextRun({
                                    text: "Text2",
                                    italics: true,
                                    bold: true,
                                    size: "10pt",
                                    break: 1

                                }),
                                new TextRun({
                                    text: "Text3",
                                    size: "10pt",
                                    break: 1

                                }),
                                new TextRun({
                                    text: "TEXT4 ",
                                    size: "10pt",
                                    break: 1
                                }),
                                new TextRun({
                                    text: "Text5",
                                    underline: {},
                                    color: "0000FF",
                                })
                            ]
                        }),
                    ],
                }),
            ],
        }),
    ],
});