UI: fix ui/build --watch

Turns out that Node's builtin fs.watch() doesn't
work on Linux. Everybody else seems to use
node-watch which has an identical API but happens
to work.

Bug: 180028167
Change-Id: I8bb0ddd561505ee02d4a8cbe85aeed5562e8ddf2
diff --git a/ui/package-lock.json b/ui/package-lock.json
index 9d805e9..2a5f87f 100644
--- a/ui/package-lock.json
+++ b/ui/package-lock.json
@@ -4205,6 +4205,12 @@
         }
       }
     },
+    "node-watch": {
+      "version": "0.7.1",
+      "resolved": "https://registry.npmjs.org/node-watch/-/node-watch-0.7.1.tgz",
+      "integrity": "sha512-UWblPYuZYrkCQCW5PxAwYSxaELNBLUckrTBBk8xr1/bUgyOkYYTsUcV4e3ytcazFEOyiRyiUrsG37pu6I0I05g==",
+      "dev": true
+    },
     "noice-json-rpc": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/noice-json-rpc/-/noice-json-rpc-1.2.0.tgz",