[manifest] added text about installable web apps (#290)

You can merge this Pull Request by running:

  git pull https://github.com/w3c/manifest installable_Web_apps

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

  https://github.com/w3c/manifest/pull/290

-- Commit Summary --

  * added text about installable web apps

-- File Changes --

    M index.html (60)

-- Patch Links --

https://github.com/w3c/manifest/pull/290.patch
https://github.com/w3c/manifest/pull/290.diff

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/manifest/pull/290