function after(code) {
    if (markdownSpace(code)) {
      effects.enter(types.blockQuotePrefixWhitespace)
      effects.consume(code)
      effects.exit(types.blockQuotePrefixWhitespace)
      effects.exit(types.blockQuotePrefix)
      return ok
    }

    effects.exit(types.blockQuotePrefix)
    return ok(code)
  }
After `>`, before optional whitespace.

```markdown
> | > a
     ^
```

@type {State}