Update Hog doc quickstart (#9495)

contents/docs/hog/index.mdx

@@ -24,6 +24,7 @@ This compatibility imposes a few key differences comparted to other programming
 - You must type out `and`, `or` and `not`. Currently `&&` and `!` raise syntax errors, whereas `||` is used as the string concatenation operator.
 - All arrays in Hog start from index `1`. Yes, for real. Trust us, we know. However that's how SQL has always worked, so we adopted it.
 - The easiest way to debug your code is to `print()` the variables in question, and then check the logs.
+- Strings must always be written with `'single quotes'`. You may use `f`-string templates like `f'Hello {name}'`.
 
 ## Syntax