Allow to add OpenSpout\Common\Entity\Cell instances as data collection values

[kusab85]

Add ability to feed FastExcel exporter (directly or via callback) with data consisting of instances of OpenSpout\Common\Entity\Cell,
which gives possibility to style every column (or even every cell) independently.

For example code like this:

$money_style = (new Style())->setCellAlignment(CellAlignment::RIGHT)->setFormat('$ # ##0.00');
$data        = [
    [
        'Employee' => 'William Smith',
        'Salary'   => Cell::fromValue(3400.00, $money_style),
        'Tax'      => Cell::fromValue(420.40, $money_style),
    ],
    [
        'Employee' => 'Dany Carey',
        'Salary'   => Cell::fromValue(4300.00, $money_style),
        'Tax'      => Cell::fromValue(220.40, $money_style),
    ],
    [
        'Employee' => 'Matt Cameron',
        'Salary'   => Cell::fromValue(3300.00, $money_style),
        'Tax'      => Cell::fromValue(222.43, $money_style),
    ],
];

(new FastExcel($data))
    ->headerStyle((new Style())->setCellAlignment(CellAlignment::CENTER)->setFontBold())
    ->configureWriterUsing(function ($writer) {
        $writer->getOptions()->setColumnWidth(20, 1);
        $writer->getOptions()->setColumnWidth(10, 2, 3);
    })
    ->export($file);

gives:

Or code like this:

$data = [
    [
        'col1' => Cell::fromValue('row1 col1', (new Style())->setFontBold()->setCellAlignment(CellAlignment::RIGHT)),
        'col2' => 'row1 col2'
    ],
    [
        'col1' => Cell::fromValue('row2 col1', (new Style())->setFontItalic()->setCellAlignment(CellAlignment::RIGHT)),
        'col2' => Cell::fromValue('row2 col2', (new Style())->setFontSize(20)->setBackgroundColor(Color::LIGHT_GREEN)),
    ],
    [
        'col1' => 'row3 col1',
        'col2' => Cell::fromValue('row3 col2', (new Style())->setBackgroundColor(Color::YELLOW)),
    ],
];

(new FastExcel($data))
    ->headerStyle((new Style())->setCellAlignment(CellAlignment::CENTER)->setFontBold())
    ->rowsStyle((new Style())->setBackgroundColor(Color::LIGHT_BLUE))
    ->configureWriterUsing( function ($writer ) {
        $writer->getOptions()->setColumnWidth(20, 1, 2);
    })
    ->export($file);

gives:

[duypdx]

@rap2hpoutre Oh I found this very helpful, could you please take a look at it for me?