Add clouds to third example

Author: HamedElgizery

src/imagery/i.sentinel/i.sentinel.coverage/i.sentinel.coverage.html

@@ -45,7 +45,7 @@ <h3>Check Sentinel-2 scenes by names</h3>
 <div class="code"><pre>
 i.sentinel.coverage settings=credentials.txt output=s2names.txt \
   names=S2A_MSIL2A_20200104T024111_N0213_R089_T49MGU_20200104T061337,S2B_MSIL2A_20200129T023939_N0213_R089_T49MGU_20200201T153252 \
-  producttype=S2MSI2A minpercent=95 area=mangkawuk
+  producttype=S2MSI2A clouds=20 minpercent=95 area=mangkawuk
 </pre></div>
 
 <h3>Use retrieved Sentinel-2 scene names for import</h3>