Added basic BMP detection & extraction

[0xda568]

This pull request adds basic support for detecting and extracting BMP (Bitmap) images as specified here:
https://learn.microsoft.com/en-us/windows/win32/gdi/bitmap-header-types

It supports bitmaps with the following DIB headers:

• BITMAPCOREHEADER
• BITMAPINFOHEADER
• BITMAPV4HEADER
• BITMAPV5HEADER

The magic value of bitmaps is "BM", so parsing and validation gets triggered quite often. To prevent a major performance impact, I tried to keep the validation as simple as possible:

1. The first header is used to perform boundary checks, which are the majority of the validation.

2. The size of the second header, which can be, if valid, on of the DIB headers above, is then checked. This is the recommended way of determining the type of the Header, as mentioned in the Microsoft documentation:

"The number of bytes required by the structure. Applications should use this member to determine which bitmap information header structure is being used."

Testing

To test it, I used a Lenovo BIOS image from a project I am working on which contains bitmaps and a lot of occurrences of "BM". I trimmed the image down to the part that contains the bitmaps and added it as a unit test:

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DECIMAL                            HEXADECIMAL                        DESCRIPTION
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
5753556                            0x57CAD4                           BMP image, total size: 270056
6093612                            0x5CFB2C                           BMP image, total size: 33236
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

As a false positive, I modified the BIOS image so that the DIB header has an invalid size:

Valid bitmap with 40 (0x28) byte DIB header:

Invalid bitmap with 0x42 byte DIB header:

The invalid image did not get detected:

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
DECIMAL                            HEXADECIMAL                        DESCRIPTION
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
5753556                            0x57CAD4                           BMP image, total size: 270056
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Thanks!