Webscrapbook

* Fixed and improved capture helpers:
* Fixed an issue that many commands do not expand parameters whose value is a command correctly.
* A selector can now reset its reference node using `base` property.
* Added "equal" command.
* "get_html" and "html" commands now support an additional `isOuter` parameter for getting and setting outer HTML.
* "match" command now supports getting named capture groups.
* "insert" command can now move nodes by specifying a selector as nodeData.
* "insert" command now supports "replace" mode.
* "insert" command now automatically escapes the content of the generated comment nodes.
* "decode_uri" command now returns the original string if the input string is malformed.
* Improved localization for zh_CN.
* Improved CSS code for several internal pages.

* Fixed fatal error when a link with an invalid URL is encountered during an in-depth capture.
* Fixed bad tidying of a CSS containing a URL with escaped newlines.
* Fixed bad tidying of a CSS containing a URL with certain escaped chars.
* Fixed bad tidying of a CSS containing a bad URL token.
* Fixed a potential error for the editor and sidebar when dealing with certain special chars.

* Fixed bad tidying of a CSS rule having an attribute selector with a `|=` operator.
* Use `text/javascript` as the default MIME type of `js` files.
* Miscellaneous improvements of the internal code and unit test suite.

* Fixed rewriting of srcset attribute that are separated by alternative spaces.
* Fixed bad URL rewriting in some complicated CSS.
* Fixed bad tidying of a CSS rule containing `:host` or `:host-context`.
* Fixed bad tidying of a CSS rule with a namespaced attribute selector.
* Fixed bad tidying of a nested CSS rule with a selector list.
* Fixed bad tidying of a resource of a font or keyframe referenced by a rule inside a shadow DOM.
* Fixed bad URL rewriting for links in an srcdoc iframe to the main page.
* Fixed bad URL hash rewriting when rebuilding links for an in-depth capture.
* Adjusted parameters handling of a content-type and content-disposition header in some rare cases.
* Miscellaneous improvements of the internal code and unit test suite.
* Added many tests for the internal API and falure tests for known issues..

* Fixed bad referrer when capturing `iframe[srcdoc]` headlessly.
* Fixed possible random errors when capturing an inaccessible `iframe[srcdoc]`.
* No more save `about:` pages for headless frames.
* No more save resources whose URL uses an unsupported protocol.
* Miscellaneous improvements of the internal code and unit test suite.
* Rewrite the unit test suite with mocha.js.

* Fixed style images in a nested CSS rule in a shadow DOM be emptied when `Style images` is `Save used` for a capture.
* Fixed style images that apppear before the first base element be emptied when `Style images` is `Save used` for a capture.
* Fixed incorrect referrer for CSS resources for a document with customized base URL for a capture.
* Miscellaneous improvements of the internal code and unit test suite.