Update README

Merge pull request #7 from kotarot/ogp

Add OGP "og:locale" (issue #3).

Add demo description and screenshot.

Correct a typo.

Merge pull request #6 from kotarot/ogp

Add OPG and thumbnail (issue #3).

Merge pull request #5 from kotarot/copy-to-clipboard

:construction: [WIP] Remove dead lines (comments) (issue #1).

Merge pull request #4 from kotarot/copy-to-clipboard

:construction: [WIP] Delete unnecessary class (issue #1).

:construction: [WIP] Add textarea to copy (issue #1).

:bug: Fix html syntax.

Initial commit.