Add BMP file support

[piotr-cz]

Closes #436

Warning: intervention/image v3 doesn't use compression when encoding bitmaps:

• https://github.com/Intervention/image/blob/3.11.5/src/Drivers/Gd/Encoders/BmpEncoder.php#L22
• https://github.com/Intervention/image/blob/3.11.5/src/Drivers/Imagick/Encoders/BmpEncoder.php#L24

[ADmad]

I don't think BMP has any place on the web :)

Merging this can potentially open a DDOS vector for existing apps given that BMPs can take up a huge amount of memory.

[piotr-cz]

I understand and I can't say that I wasn't expecting this.

Just please don't mark League\Glide\Api\Api and League\Glide\Api\Encoder classes as final, because extending these is the only way to add support for formats that are available in intervention/image.

For example psalm suggests adding @Api docblock in such case