fix: respect provided y position for addRow

[pomm0]

I figured that the current state of this addon does not allow arbitrarily setting the initial y position and will be the value of the current pdf position. Sometimes it comes handy to be able to set it, since I can set the x position too (unsure if thats supposed to do or not).

With this change it allows to define the y start position like so:

const doc = new PDFDocument({
    layout: 'landscape',
});

const imageWidth = 200;
const additionalLeftPadding = 30;

doc.image(
    `${__dirname}/sample.jpg`,
    doc.page.margins.left,
    doc.page.margins.top,
    { width: imageWidth }
);

const table = new PDFTable(doc, {
    pos: {
        y: doc.page.margins.top,  // <---- Thats the part which is working as expected now
        x: doc.page.margins.left + imageWidth + additionalLeftPadding
    }
});

table.addColumns([
    {
        id: 'product',
        header: 'Product',
        width: 70,
        padding: [5, 0],
        border: 'T',
    },
    {
        id: 'quantity',
        header: 'Quantity',
        width: 70,
        padding: [5, 0],
        border: 'T',
    },
    {
        id: 'price',
        header: 'Price',
        width: 70,
        padding: [5, 0],
        border: 'T',
    },
    {
        id: 'total',
        header: 'Total',
        width: 70,
        padding: [5, 0],
        border: 'T',
    },
]);

table.addBody([
    {product: 'Product 1', quantity: 1, price: 20.10, total: 20.10},
    {product: 'Product 2', quantity: 4, price: 4.00, total: 16.00},
    {product: 'Product 3', quantity: 2, price: 17.85, total: 35.70}
]);

Without this change:

With this change:

I could made it working with setting the y posititon of the pdf itself before creating the table (doc.y = doc.page.margins.top;), since I'm not familiar with best practises I don't know if that would be the way to go. My first intention was by passing it to the constructor, which surprisingly didn't work.