chore: address PR feedback

Author: rob

misc_docs/syntax/operator_ref_assignment.mdx

@@ -0,0 +1,45 @@
+---
+id: "ref-value-assignment"
+keywords: ["ref", "assign"]
+name: ":="
+summary: "This is the `ref value assignment` operator."
+category: "operators"
+---
+
+This operator assigns a new value to a `ref`.
+
+<CodeTab labels={["ReScript", "JS Output"]}>
+
+```res
+let total = ref(0)
+total := 1
+```
+
+```js
+var total = {
+  contents: 0
+};
+
+total.contents = 1;
+```
+
+</CodeTab>
+
+A `ref` is a builtin record type with a `mutable contents` field. Therefore the `:=` operator is just a shorthand version for the following code:
+
+<CodeTab labels={["ReScript", "JS Output"]}>
+
+```res
+let total = ref(0)
+total.contents = 1
+```
+
+```js
+var total = {
+  contents: 0
+};
+
+total.contents = 1;
+```
+
+</CodeTab>