add pdf-js viewer

webapp/views/components/Preview.js

@@ -0,0 +1,24 @@
+import { Component, h } from 'preact';
+import PDF from 'react-pdf';
+
+class Preview extends Component {
+    render(props) {
+        return (
+            <PDF
+                content={props.pdf}
+                onDocumentComplete={this._onDocumentComplete}
+                onPageComplete={this._onPageComplete}
+            />
+        );
+    }
+
+    _onDocumentComplete(pages) {
+        this.setState({pages: pages});
+    }
+
+    _onPageComplete(page) {
+        this.setState({page});
+    }
+}
+
+export default Preview;