leaflet: add version 1.6.0

https://leafletjs.com/2019/11/17/leaflet-1.6.0.html

Updated icon from https://leafletjs.com/docs/images/favicon.ico

lib/docs/scrapers/leaflet.rb

@@ -19,8 +19,13 @@ module Docs
       Maps © OpenStreetMap contributors.
     HTML
 
+    version '1.6' do
+      self.release = '1.6.0'
+      self.base_url = "https://leafletjs.com/reference-#{release}.html"
+    end
+
     version '1.5' do
-      self.release = '1.5.0'
+      self.release = '1.5.1'
       self.base_url = "https://leafletjs.com/reference-#{release}.html"
     end
 

public/icons/docs/leaflet/SOURCE

@@ -1 +1 @@
-http://leafletjs.com/docs/images/favicon.ico 
+https://leafletjs.com/docs/images/favicon.ico