[webcomponents] Add `proposals` directory. (#43)

This is a directory where we store all of in-progres proposals, summaries of work, and other documentation.
These documents were originally created on the wiki, but wiki does not have the a robust fork/PR system,
so we'll manage these manually just as part of the main repo.
You can view, comment on, or merge this pull request online at:

  https://github.com/w3c/webcomponents/pull/43

-- Commit Summary --

  * Add `proposals` directory.

-- File Changes --

    A proposals/Cross-Origin-Custom-Elements:-Concept-and-Proposal.md (164)
    A proposals/Default-Stylesheets:-Concept-and-Proposal.md (68)
    A proposals/Isolated-Imports-Proposal.md (170)
    A proposals/Limiting-the-superpowers-of-the-"Shadow-DOM-piercing-cominator".md (203)
    A proposals/Multiple-Shadow-Roots-as-"a-Shadow-Root-hosts-another-Shadow-Root".md (125)
    A proposals/Proposal-for-changes-to-manage-Shadow-DOM-content-distribution.md (228)

-- Patch Links --

https://github.com/w3c/webcomponents/pull/43.patch
https://github.com/w3c/webcomponents/pull/43.diff

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/pull/43