Desktop: Resolves #2059: Add option to transform HTML notes into Markdown (#12730)

Co-authored-by: Laurent Cozic <laurent22@users.noreply.github.com>

packages/lib/commands/convertHtmlToMarkdown.test.ts

@@ -0,0 +1,30 @@
+import { runtime } from './convertHtmlToMarkdown';
+import { CommandContext } from '../services/CommandService';
+import { defaultState } from '../reducer';
+
+const command = runtime();
+
+const makeContext = (): CommandContext => {
+	return {
+		state: defaultState,
+		dispatch: ()=>{},
+	};
+};
+
+describe('convertHtmlToMarkdown', () => {
+
+	it.each([
+		['<b>test</b>', '**test**'],
+		['<a href="https://joplin.org">Joplin</a>', '[Joplin](https://joplin.org)'],
+		['<h1>Title</h1>\n<h2>Subtitle</h2>', '# Title\n\n## Subtitle'],
+		['<ul><li>One</li><li>Two</li></ul>', '- One\n- Two'],
+		['<p>First paragraph</p><p>This is the second paragraph</p>', 'First paragraph\n\nThis is the second paragraph'],
+		['<p>A paragraph with <strong>bold</strong> and <em>italic</em></p>', 'A paragraph with **bold** and *italic*'],
+	])('should turn HTML into Markdown', async (html, markdown) => {
+		const context = makeContext();
+		const result: string = await command.execute(context, html);
+
+		expect(result).toBe(markdown);
+	});
+
+});