Delay user code by 100ms to get sensor reading (fixes #90)

libs/ev3/pxt.json

@@ -3,7 +3,8 @@
     "description": "The EV3 library",
     "files": [
         "README.md",
-        "ns.ts"
+        "ns.ts",
+        "startup.ts"
     ],
     "dependencies": {
         "base": "file:../base",

libs/ev3/startup.ts

@@ -0,0 +1,4 @@
+// This is the last thing executed before user code
+
+// We pause for 100ms to give time to read sensor values, so they work in on_start block
+loops.pause(100)