(fix) markdown newline

There were situations where the trim of the last line was not working.
sveltejs#202

src/print/doc-helpers.ts

@@ -94,7 +94,12 @@ export function trimRight(group: Doc[], isWhitespace: (doc: Doc) => boolean): Do
 }
 
 function getParts(doc: Doc): Doc[] | undefined {
-    if (typeof doc === 'object' && (doc.type === 'fill' || doc.type === 'concat')) {
-        return doc.parts;
+    if (typeof doc === 'object') {
+        if (doc.type === 'fill' || doc.type === 'concat') {
+            return doc.parts;
+        }
+        if (doc.type === 'group') {
+            return getParts(doc.contents);
+        }
     }
 }

test/printer/samples/markdown.md

@@ -17,5 +17,32 @@ by offloading the formatting of the fenced code block to prettier-plugin-svelte.
         color: green;
     }
 </style>
+```
+
+```svelte
+<script>
+    const name = "world";
+</script>
+```
 
+```svelte
+<h1>{greeting}, {name}!</h1>
+
+<style>
+    h1 {
+        color: green;
+    }
+</style>
+```
+
+```svelte
+<script>
+    const name = "world";
+</script>
+
+<h1>{greeting}, {name}!</h1>
+```
+
+```svelte
+<h1>{greeting}, {name}!</h1>
 ```