Search and include reference to the markdown text
@warning All the reference must be defined
Depth down parameter :
- -1-> every subfolder.
- 0-> the current level
- n-> (with n>0) n subfolder level of the folder
@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.
@type depth_up: integer
@param depth_up the number of upper folder to search for.
@type depth_down: integer
@param depth_down the depth to search for.