Markdown region folding (#55399)

* Add foldin g of regions to markdown

* Add test for region folding

* Tweak region identification regex

extensions/markdown-language-features/src/test/foldingProvider.test.ts

@@ -78,6 +78,31 @@ y`);
 		assert.strictEqual(firstFold.end, 2);
 	});
 
+	test('Should fold nested <!-- #region --> markers', async () => {
+		const folds = await getFoldsForDocument(`a
+<!-- #region -->
+b
+<!-- #region hello!-->
+b.a
+<!-- #endregion -->
+b
+<!-- #region: foo! -->
+b.b
+<!-- #endregion: foo -->
+b
+<!-- #endregion -->
+a`);
+		assert.strictEqual(folds.length, 3);
+		const [outer, first, second] = folds.sort((a, b) => a.start - b.start);
+
+		assert.strictEqual(outer.start, 1);
+		assert.strictEqual(outer.end, 11);
+		assert.strictEqual(first.start, 3);
+		assert.strictEqual(first.end, 5);
+		assert.strictEqual(second.start, 7);
+		assert.strictEqual(second.end, 9);
+	});
+
 });