feat(treesitter): upstream get_root_for_node() as a node method

Util from the nvim-treesitter project.

src/nvim/lua/treesitter.c

@@ -89,6 +89,8 @@ static struct luaL_Reg node_meta[] = {
   { "next_named_sibling", node_next_named_sibling },
   { "prev_named_sibling", node_prev_named_sibling },
   { "named_children", node_named_children },
+  { "root", node_root },
+
   { NULL, NULL }
 };
 
@@ -1088,6 +1090,27 @@ static int node_named_children(lua_State *L)
   return 1;
 }
 
+static int node_root(lua_State *L)
+{
+  TSNode parent;
+  TSNode result;
+
+  TSNode node;
+  if (!node_check(L, 1, &node)) {
+    return 0;
+  }
+  parent = node;
+  result = node;
+
+  while (!ts_node_is_null(parent)){
+    result = parent;
+    parent = ts_node_parent(result);
+  }
+
+  push_node(L, result, 1);
+  return 1;
+}
+
 /// assumes the match table being on top of the stack
 static void set_match(lua_State *L, TSQueryMatch *match, int nodeidx)
 {