Update README.md

Author: fussegli

README.md

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 *v0.91 March 18, 2021*\
 See release_notes.txt for a change log.
 
+**April 28 2021: code seems mature enough for publication in journal article. A new release package with current code (likely v0.92) will be created for the journal publication **\
+
 ## What is MATBOX?
 MATBOX is a MATLAB application for performing various microstructure-related tasks including **microstructure numerical generation**, **image filtering** and **microstructure segmentation**, **microstructure characterization**, **three-dimensional visualization**, **result correlation**, and **microstructure meshing**. \
 MATBOX was originally developed to analyse electrode microstructures for lithium ion batteries; however, the algorithms provided by the toolbox are widely applicable to other heterogeneous materials.