[webcomponents] Add a custom pseudo-elements proposal (#299)

You can view, comment on, or merge this pull request online at:

  https://github.com/w3c/webcomponents/pull/299

-- Commit Summary --

  * Add a custom pseudo-elements proposal

-- File Changes --

    A proposals/Custom-Pseudo-Elements.md (96)

-- Patch Links --

https://github.com/w3c/webcomponents/pull/299.patch
https://github.com/w3c/webcomponents/pull/299.diff

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/pull/299