Add built-up classifier script (sentinel-hub#218)

* add built-up classifier files

* Update script.js

Author: MaticPecovnik

Diff for: sentinel-2/built_up_classifier_mask/README.md

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+# Built-up binary classifier mask
+
+<a href="#" id='togglescript'>Show</a> script or [download](script.js) it.
+<div id='script_view' style="display:none">
+
+</div>
+
+## Evaluate and visualize
+ - [Sentinel Playground](https://apps.sentinel-hub.com/sentinel-playground/?source=S2&lat=46.95448061777255&lng=17.67425537109375&zoom=10&preset=CUSTOM&layers=B01,B02,B03&maxcc=58&gain=1.0&gamma=1.0&time=2020-03-01%7C2020-09-14&atmFilter=&showDates=false&evalscript=&evalscripturl=https://raw.githubusercontent.com/sentinel-hub/custom-scripts/master/sentinel-2/bare_soil_detector/script.js)
+ - [EO Browser](https://apps.sentinel-hub.com/eo-browser/?zoom=10&lat=46.81839&lng=17.48337&themeId=DEFAULT-THEME&datasetId=S2L2A&fromTime=2020-09-14T00%3A00%3A00.000Z&toTime=2020-09-14T23%3A59%3A59.999Z&visualizationUrl=https%3A%2F%2Fservices.sentinel-hub.com%2Fogc%2Fwms%2Fbd86bcc0-f318-402b-a145-015f85b9427e&evalscripturl=https%3A%2F%2Fraw.githubusercontent.com%2Fsentinel-hub%2Fcustom-scripts%2Fmaster%2Fsentinel-2%2Fbare_soil_detector%2Fscript.js#custom-script)
+## General description of the script
+
+The linked evalscript runs a prediction by a LightGBM classifier on the area-of-interest on L2A data. The pixel-wise probabilities are compared against a 0.8 threshold. Pixels with probabilities above this threshold are considered built-up (assigned a value of one), while others are non-built-up (assigned a zero). The mask is then expressed as a blue-tinted mask on Sentinel-2 True Color.
+
+For detailed information about the model read the [blog post](https://medium.com/p/7f2d7114ed1c/).
+
+
+## Author of the script
+
+Matic Pečovnik, Sinergise
+
+## Description of representative images
+
+Built-up classifier mask script applied on Spodnja Savinjska Region, Slovenia.
+
+Image taken on 29/06/2021.
+
+![Built-up classifier mask script applied on Spodnja Savinjska Region, Slovenia](fig/example.png)