fix autofmt: don't panic when writing blocks out without a srcfile (#2854)

* fix: don't panic when writing blocks out
* also fix serialization for hotreload
* fix windows line endings

packages/autofmt/tests/srcless/basic_expr.rsx

@@ -0,0 +1,42 @@
+    div {
+        "hi"
+        {children}
+    }
+    Fragment {
+        Fragment {
+            Fragment {
+                Fragment {
+                    Fragment {
+                        div { "Finally have a real node!" }
+                    }
+                }
+            }
+        }
+    }
+    div { class, "hello world" }
+    h1 { class, "hello world" }
+    h1 { class, {children} }
+    h1 { class, id, {children} }
+    h1 { class,
+        "hello world"
+        {children}
+    }
+    h1 { id,
+        "hello world"
+        {children}
+    }
+    Other { class, children }
+    Other { class,
+        "hello world"
+        {children}
+    }
+    div {
+        class: "asdasd",
+        onclick: move |_| {
+            let a = 10;
+            let b = 40;
+            let c = 50;
+        },
+        "hi"
+    }
+    div { class: "asd", "Jon" }