add Twoslash info and example (#1356)

Author: ethanpalm

code.mdx

@@ -77,6 +77,35 @@ class HelloWorld {
 ```
 ````
 
+### Twoslash
+
+In JavaScript and TypeScript code blocks, use `twoslash` to enable interactive type information. Users can hover over variables, functions, and parameters to see types and errors like in an IDE. 
+
+
+```ts title="Twoslash Example" twoslash
+type Pet = "cat" | "dog" | "hamster";
+
+function adoptPet(name: string, type: Pet) {
+  return `${name} the ${type} is now adopted!`;
+}
+
+// Hover to see the inferred types
+const message = adoptPet("Mintie", "cat");
+```
+
+````mdx
+```ts title="Twoslash Example" twoslash
+type Pet = "cat" | "dog" | "hamster";
+
+function adoptPet(name: string, type: Pet) {
+  return `${name} the ${type} is now adopted! 🎉`;
+}
+
+// Hover to see the inferred types
+const message = adoptPet("Mintie", "cat");
+```
+````
+
 ### Title
 
 Add a title to label your code example. Use `title="Your title"` or a string on a single line.