Plant watering system (#419)

* added youtube movie

* plant watering system

* added project entry

docs/projects/plant-watering.md

@@ -0,0 +1,40 @@
+# Plant Watering
+
+
+### ~avatar avatar
+
+Water your plants automatically!
+
+### ~
+
+https://youtu.be/7eC_VjH1eP0
+
+### ~ hint
+
+This is a follow up of the **[soil moisture project](/projects/soil-moisture)**.
+
+### ~
+
+## Materials
+
+* 1 @boardname@ with battery pack and batteries
+* 2 long nails or silver
+* 2 crocodile clips
+* 1 micro servo  + 3 female-to-croc clips
+* 1 ice cream wooden stick
+* 2 elastics
+* 1 clear tape roll
+* 1 straw
+* 1 pair of scissors
+
+## Activities
+
+* [Make](/projects/plant-watering/make)  
+* [Code](/projects/plant-watering/code)
+* [Connect](/projects/plant-watering/connect)
+
+### ~button /projects/plant-watering/make
+
+Let's get started!
+
+### ~