Deprecate relative asset paths, better warnings for asset!() (#3214)

* Deprecate relative asset paths

* fix paths, better warnings in asset parser

example-projects/ecommerce-site/src/components/loading.rs

@@ -5,7 +5,7 @@ pub(crate) fn ChildrenOrLoading(children: Element) -> Element {
     rsx! {
         document::Link {
             rel: "stylesheet",
-            href: asset!("./public/loading.css")
+            href: asset!("/public/loading.css")
         }
         SuspenseBoundary {
             fallback: |context: SuspenseContext| {

example-projects/ecommerce-site/src/main.rs

@@ -19,7 +19,7 @@ fn main() {
         rsx! {
             document::Link {
                 rel: "stylesheet",
-                href: asset!("./public/tailwind.css")
+                href: asset!("/public/tailwind.css")
             }
 
             ChildrenOrLoading {