增加占位组件：movable-area、movable-view、canvas、web-view、cover-view

src/core/view/components/canvas/index.vue

+<template>
+  <uni-canvas/>
+</template>
+<script>
+export default {
+  name: 'Canvas'
+}
+</script>

src/core/view/components/movable-area/index.vue

+<template>
+  <uni-movable-area/>
+</template>
+<script>
+export default {
+  name: 'MovableArea'
+}
+</script>

src/core/view/components/movable-view/index.vue

+<template>
+  <uni-movable-view/>
+</template>
+<script>
+export default {
+  name: 'MovableView'
+}
+</script>

src/platforms/h5/view/components/cover-view/index.vue

+<template>
+  <uni-cover-view/>
+</template>
+<script>
+export default {
+  name: 'CoverView'
+}
+</script>

src/platforms/h5/view/components/web-view/index.vue

+<template>
+  <uni-web-view/>
+</template>
+<script>
+export default {
+  name: 'WebView'
+}
+</script>