[ServiceWorker] Grammatical fix (#591)

You can merge this Pull Request by running:

  git pull https://github.com/zg/ServiceWorker patch-1

Or you can view, comment on it, or merge it online at:

  https://github.com/slightlyoff/ServiceWorker/pull/591

-- Commit Summary --

  * Grammatical fix

-- File Changes --

    M explainer.md (2)

-- Patch Links --

https://github.com/slightlyoff/ServiceWorker/pull/591.patch
https://github.com/slightlyoff/ServiceWorker/pull/591.diff

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Reply to this email directly or view it on GitHub:
https://github.com/slightlyoff/ServiceWorker/pull/591