add comment specifying edgecase of server function prefixes (#2345)

leptos_macro/src/lib.rs

@@ -869,7 +869,8 @@ pub fn slot(args: proc_macro::TokenStream, s: TokenStream) -> TokenStream {
 /// You can provide any combination of the following named arguments:
 /// - `name`: sets the identifier for the server function’s type, which is a struct created
 ///    to hold the arguments (defaults to the function identifier in PascalCase)
-/// - `prefix`: a prefix at which the server function handler will be mounted (defaults to `/api`)
+/// - `prefix`: a prefix at which the server function handler will be mounted (defaults to `/api`) 
+///    your prefix must begin with `/`. Otherwise your function won't be found.
 /// - `endpoint`: specifies the exact path at which the server function handler will be mounted,
 ///   relative to the prefix (defaults to the function name followed by unique hash)
 /// - `input`: the encoding for the arguments (defaults to `PostUrl`)