This function take a file, load the content, create a backup (if needed)
and do some change in the file which is supposed to be a markdown file.
Then saved the new file with the same filename. The goal is to beautify
the markdown file.
@type filename: string
@param filename: The name and path of the file to work with. This file is
supposed to be a markdown file.
@type backup_option: boolean
@param backup_option: This parameter is set to true by default.
If the backup option is set,
then a file named filename.bak will be created.
@type filename_ext: string
@param filename_ext: This parameter the markdown extension
for the filename.
@return nothing