feat: enhance learning materials with escape sequences and additional context

- Add escape sequences to the FINISHED.mdx file, explaining their role in string manipulation.
- Update README for the template literals exercise to include a note about future content on functions.

Author: kentcdodds

exercises/01.expressions-and-output/05.solution.template-literals/README.mdx

@@ -11,3 +11,5 @@ as you write more code.
 // You can even call functions inside template literals
 console.log(`Random number: ${Math.random()}`)
 ```
+
+We'll get to functions later.

exercises/01.expressions-and-output/FINISHED.mdx

@@ -7,6 +7,7 @@ You learned:
 - 🖨️ **console.log()** prints values to the terminal so you can see results
 - 🏃 **Running code** with `node index.ts` executes your TypeScript file
 - 📝 **String expressions** create text values using quotes
+- 🔄 **Escape sequences** include special characters in strings like `\n` for newlines
 - ➕ **String concatenation** joins strings together with `+`
 - 🔢 **Number expressions** and arithmetic operators (`+`, `-`, `*`, `/`)
 - 💬 **Template literals** use backticks and `${expression}` for interpolation