Update README.md

Author: cordmaur

README.md

@@ -18,6 +18,14 @@ All the details and tests has been described in the article <b>Automatic Water D
 Cordeiro, M. C. R.; Martinez, J.-M.; Peña-Luque, S. Automatic Water Detection from Multidimensional Hierarchical Clustering for Sentinel-2 Images and a Comparison with Level 2A Processors. Remote Sensing of Environment 2021, 253, 112209. https://doi.org/10.1016/j.rse.2020.112209.
 
 ## Changelog
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+### Release 1.5.9
+- Added external mask processing through the command `process_ext_masks`. It prepares an external mask (ex. created by FMask) to be used by WaterDetect.
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+### Release 1.5.8
+- correct GlintMode to work on S2_THEIA images
+- Add calculation of MBWI index inside DWImageClustering class
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 ### Release 1.5.7 
 - new entry point runWaterDetect.py 
 - Namespace correction for different versions of sklearn package