updated Description file

solved issue massimoaria#38

bibliometrix v2.1.0

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New functionality:
* biblioshiny networks are now plotted using VisNetwork package.
* biblioshiny menu have been completely rewritten. Now, descriptive analyses are organized by the unit of analysis
* Several descriptive plots and tables have been added
* Added the new funtion authorProdOverTime to calclulate and plot the productivity over the time of the top authors
* Added "measure" parameter in plotThematicEvolution
* Added the new function bib2df. It give the possibility to import data from a "generic" bibtex file format  (i.e. Zotero, JabRef, etc.)
* Added the possibility to calculate H-index for sources

Added "measure" parameter in plotThematicEvolution

updated NEWS file

version 2.0.1

version 2.0.1

minor fix