nvim: update yamlls with reference tag

nvim/lsp/yamlls.lua

@@ -4,7 +4,7 @@ return {
   filetypes = {
     "yaml",
     "yaml.docker-compose",
-    -- "yaml.gitlab",
+    "yaml.gitlab",
     "yaml.helm-values",
   },
   root_markers = {
@@ -21,6 +21,9 @@ return {
       format = {
         enable = true,
       },
+      customTags = {
+        "!reference sequence",
+      },
     },
   },
 }