js-info polishing

[Per Bothner]

I think I've gotten my changes to the js-info reader to a state where it
can be checked in.  See attachment.

In addition to the a "Hide sidebar"/"Show sidebar" button (lower left),
there is also magic to handle narrows screen better, including auto-hide
of the sidebar.

        * js/info.js: Add button to show/hide sidebar.  Other polishing.
        (Sidebar): Create show/hide button.
        (on_click): Handle clicks on show/hide button.
        Also automatically hide sidebar on click when narrow.
        (Sidebar): Copy _href property when copying ToC.
        * js/info.css: Various adjustments and tricks to make it work.

This is the DomTerm manual with some extra DomTerm css style tweaks.
https://per.bothner.com/tmp/DomTerm-txjs/

This is the same manual with just the default styling from info.css:
https://per.bothner.com/tmp/DomTerm-txjs-plain

Please try with different window sizes.
Suggestions/comments about either style appreciated.
--
        --Per Bothner
per@bothner.com   http://per.bothner.com/

jsinfo1.patch
Description: Text Data