Add useGroupLookup hook

app/soapbox/hooks/api/groups/useGroupLookup.ts

@@ -0,0 +1,17 @@
+import { Entities } from 'soapbox/entity-store/entities';
+import { useEntityLookup } from 'soapbox/entity-store/hooks';
+import { useApi } from 'soapbox/hooks/useApi';
+import { groupSchema } from 'soapbox/schemas';
+
+function useGroupLookup(slug: string) {
+  const api = useApi();
+
+  return useEntityLookup(
+    Entities.GROUPS,
+    (group) => group.slug === slug,
+    () => api.get(`/api/v1/groups/lookup?name=${slug}`),
+    { schema: groupSchema },
+  );
+}
+
+export { useGroupLookup };