Add strong and em formatting support to PlainTextRenderer when allowSimpleMarkdown is true

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: Copilot

src/github/markdownUtils.ts

@@ -287,9 +287,15 @@ export class PlainTextRenderer extends marked.Renderer {
 		return content;
 	}
 	override strong(text: string): string {
+		if (this.allowSimpleMarkdown) {
+			return `**${text}**`;
+		}
 		return text;
 	}
 	override em(text: string): string {
+		if (this.allowSimpleMarkdown) {
+			return `*${text}*`;
+		}
 		return text;
 	}
 	override codespan(code: string): string {

src/test/github/markdownUtils.test.ts

@@ -31,4 +31,40 @@ suite('PlainTextRenderer', () => {
 		const result = marked.parse('rename the `Foo` class to `Bar`', { renderer, smartypants: true });
 		assert.strictEqual(result.trim(), 'rename the \\`Foo\\` class to \\`Bar\\`');
 	});
+
+	test('should strip strong formatting by default', () => {
+		const renderer = new PlainTextRenderer();
+		const result = marked.parse('This is **bold** text', { renderer, smartypants: true });
+		assert.strictEqual(result.trim(), 'This is bold text');
+	});
+
+	test('should preserve strong formatting when allowSimpleMarkdown is true', () => {
+		const renderer = new PlainTextRenderer(true);
+		const result = marked.parse('This is **bold** text', { renderer, smartypants: true });
+		assert.strictEqual(result.trim(), 'This is **bold** text');
+	});
+
+	test('should strip em formatting by default', () => {
+		const renderer = new PlainTextRenderer();
+		const result = marked.parse('This is *italic* text', { renderer, smartypants: true });
+		assert.strictEqual(result.trim(), 'This is italic text');
+	});
+
+	test('should preserve em formatting when allowSimpleMarkdown is true', () => {
+		const renderer = new PlainTextRenderer(true);
+		const result = marked.parse('This is *italic* text', { renderer, smartypants: true });
+		assert.strictEqual(result.trim(), 'This is *italic* text');
+	});
+
+	test('should handle combined formatting when allowSimpleMarkdown is true', () => {
+		const renderer = new PlainTextRenderer(true);
+		const result = marked.parse('rename the `Foo` class to **`Bar`** and make it *italic*', { renderer, smartypants: true });
+		assert.strictEqual(result.trim(), 'rename the `Foo` class to **`Bar`** and make it *italic*');
+	});
+
+	test('should strip all formatting by default', () => {
+		const renderer = new PlainTextRenderer(false);
+		const result = marked.parse('rename the `Foo` class to **`Bar`** and make it *italic*', { renderer, smartypants: true });
+		assert.strictEqual(result.trim(), 'rename the \\`Foo\\` class to \\`Bar\\` and make it italic');
+	});
 });