add js_newthread.ml; make newthread_page beautiful

src/dune

@@ -50,6 +50,16 @@
  (preprocess
   (pps js_of_ocaml-ppx)))
 
+(executable
+ (name js_newthread)
+ (modules js_newthread)
+ (libraries js_of_ocaml brr)
+ (modes js)
+ (js_of_ocaml
+  (javascript_files leaflet/leaflet.js))
+ (preprocess
+  (pps js_of_ocaml-ppx)))
+
 (executable
  (name js_thread)
  (modules js_thread)
@@ -114,6 +124,7 @@
   (source_tree content)
   (file content/assets/js/js_plant_map.js)
   (file content/assets/js/js_babillard.js)
+  (file content/assets/js/js_newthread.js)
   (file content/assets/js/js_thread.js))
  (action
   (with-stdout-to