Add clipboard IDL description. (#158)

* Add clipboard IDL description.

* Fix bikeshed error.

* Address comments.

* Fix error.

* Fix error.

* Revert "Address comments."

This reverts commit 8cd8570.

* Address comments.

* Address comments.

* Addressed review comments.

* Address review comments.

* Add conversion of DOMString to Blob type.

* Address PR comments.

* Addressed comments.

* Address PR comments.

* Fix bikeshed error.

* Address PR comments.

* Address PR comments.

* Address PR comments.

* Address review comments.

* Address more review comments.

* Address review comments.

* Address review comments.

* Address PR comments.

* Address PR comments.

* Address PR comments.

* Address comments.

* Address comments.

* Address comments.

* Address comments.

* Address PR comments.

* Address comment.