agenda+ Changes to Web Authoring techniques page

I moved the table of contents to the side.  It also slides with the content.
I renamed the Text Direction section as Bidirectional Text, and moved 
the Vertical Text subsection to Styling & Layout.
I renamed Composite Messages & Re-use subsection as Working With Strings 
In JavaScript & Databases.

https://w3c.github.io/i18n-drafts/techniques/authoring-html.en

Just proposing an agenda slot in case anyone wants to make any 
observations before i make it live on CVS.

ri