Adding water surface visualizer to the sentinel 2 custom scripts repo (sentinel-hub#217)

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* Update README.md

* Create script.js

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* Create script.js

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Author: hareldunn

sentinel-2/water_surface_visualizer/README.md

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+# Water Surface Visualizer
+<a href="#" id='togglescript'>Show</a> V3 script or [download](script.js){:target="_blank"} it.
+<div id='script_view' style="display:none">
+{% highlight javascript %}
+      {% include_relative script.js %}
+{% endhighlight %}
+</div>
+
+## Evaluate and visualize
+
+ - [Sentinel Playground](https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=35.174032839292316&lng=35.90675354003906&zoom=12&preset=CUSTOM&layers=B01,B02,B03&maxcc=87&gain=1.0&gamma=1.0&time=2021-03-01%7C2021-09-10&atmFilter=&showDates=false&evalscript=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%3D%3D){:target="_blank"}    
+
+
+## Author of the script
+[@HarelDan](https://twitter.com/HarelDan){:target="_blank"}    
+
+## General description of the script
+The script uses the small spectral changes found between adjacent bands to highlight areas of variance
+in and otherwise homogemuous region. This tool works best on flat water surface, and can highlight water
+eddies, temperature induced vortices, suspended matter in shallow water, oil slicks and sheens, and more.
+
+## Description of representative images
+
+Water surface artefacs near Baniyas refinery, Syria.
+There has been an ongoing man-made disaster with petroleum distilates spilling into the mediterraen and flowig as far as Cyprus/
+
+
+![Oils spill outside Baniyas refinery, Syria](figs/baniyas.jpg)
+
+## References
+Based on: 
+[source 1](https://twitter.com/HarelDan/status/1483415093014634499){:target="_blank"}, 
+
+
+
+

sentinel-2/water_surface_visualizer/figs/baniyas.jpg

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+//VERSION=3
+
+/*
+
+Sentinel-2 Water Surface Visualizer
+Author: Harel Dan (https://www.linkedin.com/in/harel-dan, https://twitter.com/HarelDan)
+
+The script uses the small spectral changes found between adjacent bands to highlight areas of variance
+in and otherwise homogemuous region. This tool works best on flat water surface, and can highlight water
+eddies, temperature induced vortices, suspended matter in shallow water, oil slicks and sheens, and more.
+
+*/
+
+var v1 = Math.log((B02/B03)); 
+var v2 = Math.log((B03/B04));
+var v3 = Math.log((B04/B08));
+
+return [v1,v2,v3];
+
+// alternatively, one can enhace the green band fraction slightly more, by multiplying v1 with v2 in the R band
+// return [v1*v2,v2,v3];