Adjust technical/bitmap-format to be formatted by AsciiDoc, and
add some missing information to the documentation.
source: <pull.1246.v4.git.1655355834.gitgitgadget@gmail.com>
* ac/bitmap-format-doc:
bitmap-format.txt: add information for trailing checksum
bitmap-format.txt: fix some formatting issues
bitmap-format.txt: feed the file to asciidoc to generate html