fix: Escape characters visible in TOC

closes #1226

shared/utils/getHeadingsForText.test.js

@@ -0,0 +1,23 @@
+/* eslint-disable flowtype/require-valid-file-annotation */
+import getHeadingsForText from './getHeadingsForText';
+
+it('should return an array of document headings', () => {
+  const response = getHeadingsForText(`
+# Header
+  
+## Subheading
+`);
+
+  expect(response.length).toBe(2);
+  expect(response[0].level).toBe(1);
+  expect(response[0].title).toBe('Header');
+  expect(response[1].level).toBe(2);
+  expect(response[1].title).toBe('Subheading');
+});
+
+it('should unescape special characters', () => {
+  const response = getHeadingsForText(`# Header <\\>`);
+
+  expect(response.length).toBe(1);
+  expect(response[0].title).toBe('Header <>');
+});