Allow to attach all files from directories as attachments

[discordier]

When generating complex assets, like HTML reports, it is tedious to attach them one-by-one.

For example, the coverage report of phpunit spans lots of sub-directories and all sorts of files, like CSS, SVG, JS.

I therefore suggest to add something along the lines of:

<?php

declare(strict_types=1);

namespace Phpcq\PluginApi\Version11\Report;

use Phpcq\PluginApi\Version10\Exception\RuntimeException;
use Phpcq\PluginApi\Version10\Report\AttachmentBuilderInterface as AttachmentBuilderInterface10;

interface AttachmentBuilderInterface extends AttachmentBuilderInterface10
{
    /**
     * Load the contents from a reachable directory.
     *
     * @param string $directory The absolute path to the directory.
     *
     * @return $this
     *
     * @throws RuntimeException When the path is not absolute.
     */
    public function fromDirectory(string $directory): self;
}

I am unsure how to determine the mimetypes, though.

An alternative approach would be to collect the directory contents as zip file, they won't be browsable then though.