Rework definition import to support multiple files and imports, nested messages, add configuration export/import

src/app/editor/editor.component.html

@@ -10,8 +10,10 @@
   } }
 </div>
 
+@if(showRaw()) {
 <h2>Preview</h2>
 <div class="actions">
   <button mat-flat-button (click)="copyToClipboard()">Copy</button>
 </div>
-<pre *ngIf="showRaw()"><code #code></code></pre>
+<pre><code #code></code></pre>
+}

src/app/editor/editor.component.scss

@@ -11,7 +11,7 @@ div {
 }
 
 div {
-  padding: 10px;
+  padding: 16px;
 }
 
 .actions {