chore: get codesandbox examples working again (storacha#292)

- codesansbox ci now support node 18
- disable `buildCommand` as it is done after install by the prepare
lifecycle script

see: https://codesandbox.io/docs/learn/sandboxes/ci#configuration-format

fixes storacha#237

note: there is an issue to consolidate the examples in storacha#256 but our
current set of examples are linked to from beta.ui.web3.storage so if we
can get them working again without too much pain I think we should.

License: MIT
Signed-off-by: Oli Evans <oli@protocol.ai>

Signed-off-by: Oli Evans <oli@protocol.ai>
Co-authored-by: Travis Vachon <travis.vachon@gmail.com>

.codesandbox/ci.json

@@ -1,4 +1,5 @@
 {
+  "buildCommand": false,
   "sandboxes": [
     "/examples/react/file-upload",
     "/examples/react/sign-up-in",
@@ -11,5 +12,5 @@
     "/examples/vue/uploads-list"
   ],
   "packages": ["packages/**"],
-  "node": "16"
+  "node": "18"
 }