[Docs] Add migration example for relations with wrapped components (#4595)

## Description

Discussion #4418 pointed out that the upgrade guide doesn't cover
migrating `withRef` + `simultaneousHandlers` on wrapped components like
`ScrollView`. This adds a short subsection under "Migrating relations"
with a code comparison and a table mapping `simultaneousHandlers`,
`waitFor` and `blocksHandlers` to `simultaneousWith`, `requireToFail`
and `block`.

Also makes the tables in the upgrade guide use `table-layout: fixed` so
the two columns are split evenly. The rule is scoped to this page, all
of its tables are two-column RNGH2 to RNGH3 maps.

## Test plan

Read docs 🤓

Author: m-bert

packages/docs-gesture-handler/docs/guides/upgrading-to-3.mdx

@@ -238,6 +238,38 @@ Full changes are as follows:
 | `gesture.requireExternalGestureToFail`    | `gesture.requireToFail`     |
 | `gesture.blocksExternalGesture`           | `gesture.block`             |
 
+### Relations with wrapped components
+
+Previously, relation properties of [wrapped components](/docs/components/wrapped-components), such as `ScrollView`, accepted refs, so the gesture had to be assigned a ref using `withRef`. In Gesture Handler 3, those properties accept gesture objects directly, and `withRef` is no longer needed.
+
+<CodeComparison
+label1={"RNGH 2"}
+label2={"RNGH 3"}
+code1={
+`const panRef = useRef();
+const pan = Gesture.Pan().withRef(panRef);
+
+<GestureDetector gesture={pan}>
+  <ScrollView simultaneousHandlers={panRef} />
+</GestureDetector>
+`}
+code2={
+`const pan = usePanGesture({});
+
+<GestureDetector gesture={pan}>
+  <ScrollView simultaneousWith={pan} />
+</GestureDetector>
+`}
+/>
+
+Full changes are as follows:
+
+| RNGH2                  | RNGH3                  |
+| ---------------------- | ---------------------- |
+| `simultaneousHandlers` | `simultaneousWith`     |
+| `waitFor`              | `requireToFail`        |
+| `blocksHandlers`       | `block`                |
+
 
 ## Migrating components relying on view hierarchy
 

packages/docs-gesture-handler/src/css/overrides.css

@@ -28,6 +28,11 @@ table thead tr {
   border-bottom: 1px solid var(--ifm-table-border-color);
 }
 
+/* Every table in the upgrade guide maps RNGH2 to RNGH3, so split the columns evenly. */
+.docs-doc-id-guides\/upgrading-to-3 table {
+  table-layout: fixed;
+}
+
 .platform-compatibility table {
   display: table;
   width: 100%;