Add preview marker to documentation link

Co-authored-by: Iván Cea Fontenla <[email protected]>

Author: mjmbischoff

docs/reference/query-languages/esql/_snippets/lists/mv-functions.md

@@ -1,7 +1,7 @@
 * [`MV_APPEND`](../../functions-operators/mv-functions.md#esql-mv_append)
 * [`MV_AVG`](../../functions-operators/mv-functions.md#esql-mv_avg)
 * [`MV_CONCAT`](../../functions-operators/mv-functions.md#esql-mv_concat)
-* [`MV_CONTAINS`](../../functions-operators/mv-functions.md#esql-mv_contains)
+* [preview] [`MV_CONTAINS`](../../functions-operators/mv-functions.md#esql-mv_contains)
 * [`MV_COUNT`](../../functions-operators/mv-functions.md#esql-mv_count)
 * [`MV_DEDUPE`](../../functions-operators/mv-functions.md#esql-mv_dedupe)
 * [`MV_FIRST`](../../functions-operators/mv-functions.md#esql-mv_first)