feat(import/markdown): import in-display math properly

src/services/import/markdown.spec.ts

@@ -163,4 +163,16 @@ second line 2</code></pre><ul><li>Hello</li><li>world</li></ul><ol><li>Hello</li
         expect(markdownService.renderToHtml(input, "Title")).toStrictEqual(expected);
     });
 
+    it("converts inline math expressions into Mathtex format", () => {
+        const input = `The equation is\u00a0$e=mc^{2}$.`;
+        const expected = /*html*/`<p>The equation is&nbsp;<span class="math-tex">\(e=mc^{2}\)</span>.</p>`;
+        expect(markdownService.renderToHtml(input, "Title")).toStrictEqual(expected);
+    });
+
+    it("converts display math expressions into Mathtex format", () => {
+        const input = `$$\sqrt{x^{2}+1}$$`;
+        const expected = /*html*/`<p><span class="math-tex">\\[\sqrt{x^{2}+1}\\]</span></p>`;
+        expect(markdownService.renderToHtml(input, "Title")).toStrictEqual(expected);
+    });
+
 });

src/services/import/markdown.ts

@@ -12,7 +12,13 @@ class CustomMarkdownRenderer extends Renderer {
     }
 
     paragraph(data: Tokens.Paragraph): string {
-        return super.paragraph(data).trimEnd();
+        let text = super.paragraph(data).trimEnd();
+
+        // Display math
+        text = text.replaceAll(/\$\$(.+)\$\$/g,
+            `<span class="math-tex">\\\[$1\\\]</span>`);
+
+        return text;
     }
 
     code({ text, lang }: Tokens.Code): string {