Dynamically sized page margin content

If i have na element defined as `running` at the top of the page, and the content of this element is bigger than the page margin i get result where the header overflows the body.

Of course i could just increase the margin, but in my case, the header will be dynamic, and there is no way to know how big it can be..

## Screenshot
### Page 1

### Page 2

## Reproducible code:

```

* {
font-family: 'Arial';
}
@page {
size: A4;
font-size: 16px;
margin: 2cm;

@top-center {
content: element(header);
}

@bottom-center {
content: element(footer);
}
}
.header {
page-break-inside: avoid;
position: running(header);
}
.footer {
page-break-inside: avoid;
position: running(footer);
}
table {
width: 100%;
font-size: 16px;
margin: 1cm;
border-collapse: collapse;
}

td, th {
padding: 6px;
border: 1px solid gray;
}
tfoot td {
background-color: aqua;
}
thead th {
background-color: coral;
}

Title 1Title 2


HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloWorld!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloWorld!
HelloWorld!
HelloWorld!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!
HelloHello World! Hello World! Hello World!
Hello World! Hello World! Hello World!
HelloWorld!
HelloWorld!

```