Markdown support for TextPreviews (#396)

* add markdown-to-jsx dependency

* replace TextPreview with Markdown

* basic table styling

* add light mode backgroundColor

frontend/src/styles/global.style.tsx

@@ -3,11 +3,20 @@ import { Global } from "@mantine/core";
 const GlobalStyle = () => {
   return (
     <Global
-      styles={() => ({
+      styles={(theme) => ({
         a: {
           color: "inherit",
           textDecoration: "none",
         },
+        "table.md, table.md th:nth-of-type(odd), table.md td:nth-of-type(odd)": {
+          background: theme.colorScheme == "dark"
+            ? "rgba(50, 50, 50, 0.5)"
+            : "rgba(220, 220, 220, 0.5)",
+        },
+        "table.md td": {
+          paddingLeft: "0.5em",
+          paddingRight: "0.5em",
+        },
       })}
     />
   );