Can't use Promise in template expression

[Rich-Harris]

Side-issue to #1440 — you can't use Promise in a template expression without declaring it as a helper (or as data). It should be among the whitelisted globals:

{#await Promise.resolve(42)}
  <p>waiting...</p>
{:then answer}
  <p>the answer is {answer}</p>
{/await}

{#if true}
  <p>true!</p>
{/if}

<!-- the script block should be unnecessary -->
<script>
  export default {
    helpers: { Promise }
  };
</script>

[acstll]

I could try a "good first issue" kind of PR, it should be adding 'Promise' about there:

svelte/src/utils/globalWhitelist.ts

Line 21 in ddf2d9d

'parseInt',

no?

[Rich-Harris]

exactly — that'd be awesome, thank you!