Inherit page margins from active sheet

[Bird87ZA]

This is:

- [ ] a bug report
- [x] a feature request
- [ ] **not** a usage question (ask them on https://stackoverflow.com/questions/tagged/phpspreadsheet or https://gitter.im/PHPOffice/PhpSpreadsheet)

What is the expected behavior?

Page margins get inherited from the active sheet

What is the current behavior?

Page margins are ignored completely

What are the steps to reproduce?

Please provide a Minimal, Complete, and Verifiable example of code that exhibits the issue without relying on an external Excel file or a web server:

<?php

require __DIR__ . '/vendor/autoload.php';

// Create new Spreadsheet object
$spreadsheet = new \PhpOffice\PhpSpreadsheet\Spreadsheet();

$sheet = $spreadsheet->getActiveSheet();
$sheet->getPageSetup()->setOrientation(\PhpOffice\PhpSpreadsheet\Worksheet\PageSetup::ORIENTATION_LANDSCAPE);
$sheet->getPageMargins()
    ->setLeft(0.1)
    ->setRight(0.1)
    ->setTop(0.1)
    ->setBottom(0.1)
    ->setHeader(0);
$sheet->setCellValue('A1', 'Test input');

$writer = new \PhpOffice\PhpSpreadsheet\Writer\Pdf\Mpdf($spreadsheet);
$writer->save('test.pdf');

Which versions of PhpSpreadsheet and PHP are affected?

All

[Bird87ZA]

I'm busy with a pull request for this improvement.