[Doc] extend description for "FoE Register File Indications" for files with wildcard

Add explanation for new featur FoE Register for files with wildcard to documentation:

The FoE register file indications service can be used either to register individual file name or use the characters ‘*’ and ‘?’ to specify all file names matching the mask.
For example, patterns like ‘*.zip’ , '*.fw' or 'fw????.zip' can be used for the parameter ‘abFilename’ of the service to cover the device requirements.
The registered pattern will be compared with all files that are loaded via FoE. The transfer will be allowed and the host application will receive the indication from EtherCAT stackf, if the name of the transferred file corresponds to the pattern.

Note, that following templates are reserved and can't be registered: ‘fwupdate.zip’, ‘*.nxi’, ‘*.nxe’, ‘*.nai’, ‘*.nae’, ‘*.nxs’, these are allowed via FoE for netX by default. The patterns like ‘*\\\*’, "**" are not supported.