feat: enable onload callbacks (#414)

* refactor(examples): run ssr example from server

* chore: switch to babel for build

buble complains too much

* feat: enable loaded callbacks

feat: add skip option

* examples: add async-callback browser example

* examples: fix server

* examples(ssr): add reactive script with callback

* fix: also skip on ssr

* chore: remove unused var

* feat: only add mutationobserver if DOM is still loading

feat: disconnect mutation observer once DOM has loaded

* examples: pass vmid to loadCallback instead of el

* feat: also support load callbacks for link/style tags

* test: add unit tests for load

* test: add load e2e test

* chore: fix lint

* chore: remove unused files

* test: fix e2e load callback test

* test: fix attempt

* examples: ie9 compatiblity

destructuring doesnt work in ie9

* fix: add onload attribute on ssr

dont rely on mutationobserver

* chore: lint ci conf

* refactor: remove loadCallbackAttribute config option

test: fix coverage for load

* test: improve coverage

* fix: only use console when it exists (for ie9)

* chore: fix coverage

test/fixtures/app.template.html

@@ -5,7 +5,7 @@
     {{ title.text() }}
     {{ link.text() }}
     {{ style.text() }}
-    {{ webpackAssets }}
+    {{ headAssets }}
     {{ script.text() }}
     {{ noscript.text() }}
   </head>
@@ -13,6 +13,7 @@
     {{ script.text({ pbody: true }) }}
     {{ noscript.text({ pbody: true }) }}
     {{ app }}
+    {{ bodyAssets }}
     {{ script.text({ body: true }) }}
     {{ noscript.text({ body: true }) }}
   </body>