Ability to set header image for a Page (#6210)

* Ability to set header image for a Page

 - Add header image to Page
 - Show it on Page view
 - Show correctly it on Page list view
 - On the Page list view, pages have a light border
   to make it easier to see an image belongs to a page

* Maybe it looks better

* Use <img> instead if <x-image>

* src -> :src; set width

* Update page.vue

Co-authored-by: syuilo <Syuilotan@yahoo.co.jp>

src/client/pages/page.vue

@@ -5,6 +5,7 @@
 
 	<div class="_card" v-if="page" :key="page.id">
 		<div class="_title">{{ page.title }}</div>
+		<img class="header" :src="page.eyeCatchingImage.url" v-if="page.eyeCatchingImageId" />
 		<div class="_content">
 			<x-page :page="page"/>
 		</div>
@@ -115,6 +116,8 @@ export default Vue.extend({
 
 <style lang="scss" scoped>
 .xcukqgmh {
-
+	> ._card > .header {
+		max-width: 100%;
+	}
 }
 </style>