Add configs for bitmap image files (`.bmp`)

Ensure that `.bmp` files will:

 * be served with the `image/bmp` media type (which is not registered
   at IANA, but is used by recent versions of Apache and seems to be
   the most commonly used according to the HTTP Archive¹)
 * be served compressed (BMP image formats² are either not natively
   compressed, or use RLE compression which achieves poor compression
   ratios, therefore, they compress quite nicely)
 * be served with far future expires headers
 * not be served with any of the `HTML` document related headers

Note:

  * While BMP images are not a suitable image format for the web, a
    decent number of sites still use them.

    e.g.: Looking into the HTTP Archive¹ at the results from 01.09.2014,
    4676 requests were made to BMP images, 4447 (~95.10%) of them being
    served uncompressed.

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¹ https://www.igvita.com/2013/06/20/http-archive-bigquery-web-performance-answers/
² https://en.wikipedia.org/wiki/BMP_file_format