Added a note about ref usage in Oxpecker.Solid

src/Oxpecker.Solid/README.md

@@ -73,6 +73,8 @@ This library doesn't provide support for React-like context. I strongly believe
 
 Note that `attr:`, `on:`, `bool:`, `ref` attributes are exposed as F# methods in the API: `elem.on(...)`, `elem.attr(...)` etc. Also, `style` and `class'` are attributes when accepting `string`, while `style'` and `classList` are methods when accepting `object` (to be used with [createObj](https://fable.io/docs/javascript/features.html#createobj)).
 
+_Note_: when using `ref(nativeElem)` make sure that `nativeElem` is mutable (e.g. `let mutable nativeElem = Unchecked.defaultof<HTMLDivElement>`).
+
 ### Store
 
 Similar to the original implementation in `Fable.Solid` , store has a special helper for updating its fields:
@@ -88,7 +90,6 @@ setStore // store setter
 Again, just as in the original implementation in `Fable.Solid`, resource is a special object, so instead of JS `resource()` call, you'll need to use `resource.current` in F#.
 
 
-
 ### Router
 
 Router namespace is `Oxpecker.Solid.Router`. It contains router related components and functions. To render a router you still need to decorate router function with `SolidComponent` attribute:

tests/Oxpecker.Solid.Tests/SolidCases/Refs/Refs.expected

@@ -3,7 +3,7 @@ import { onMount } from "solid-js";
 import { some } from "./fable_modules/fable-library-js.4.23.0/Option.js";
 
 export function Test() {
-    const htmlCanvas = defaultOf();
+    let htmlCanvas = defaultOf();
     onMount(() => {
         console.log(some(htmlCanvas.height + htmlCanvas.width));
     });

tests/Oxpecker.Solid.Tests/SolidCases/Refs/Refs.fs

@@ -7,9 +7,9 @@ open Fable.Core.JS
 
 [<SolidComponent>]
 let Test () =
-    let htmlCanvas: HTMLCanvasElement = Unchecked.defaultof<_>
+    let mutable htmlCanvas: HTMLCanvasElement = Unchecked.defaultof<_>
     onMount(fun () -> console.log(htmlCanvas.height + htmlCanvas.width))
 
-    div().ref(fun _ -> console.log("before mounted")) {    
+    div().ref(fun _ -> console.log("before mounted")) {
         canvas(width=256, height=256).ref(htmlCanvas)
     }