Enlist all file names in a folder and it's subfolders

This function enlist all files from given folder & it's sub-folders with given extensions

This is useful function in case you want to enlist all files from a folder and it's sub-folder with given file extension list.

Input argument is the folder name with complete path as a string(e.g. '/media/Nitin/SSA/FolderName').

Output is a variable containing list of all files along with complete path.

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