Update `html5.nav-toc` description
Update `html5.nav-toc` description

Clarify description & add a trailing period to separate it from the stem sentence with the list of supported values generated by docs `resources/params.xsl`.

infotexture/dita-ot,dita-ot/dita-ot,robander/dita-ot,dita-ot/dita-ot,doctales/dita-ot,drmacro/dita-ot,eerohele/dita-ot,eerohele/dita-ot,shaneataylor/dita-ot,Hasimir/dita-ot,drmacro/dita-ot,doctales/dita-ot,dita-ot/dita-ot,doctales/dita-ot,shaneataylor/dita-ot,eerohele/dita-ot,shaneataylor/dita-ot,doctales/dita-ot,drmacro/dita-ot,robander/dita-ot,infotexture/dita-ot,Hasimir/dita-ot,Hasimir/dita-ot,infotexture/dita-ot,drmacro/dita-ot,shaneataylor/dita-ot,infotexture/dita-ot,shaneataylor/dita-ot,robander/dita-ot,dita-ot/dita-ot,drmacro/dita-ot,robander/dita-ot,infotexture/dita-ot,eerohele/dita-ot,dita-ot/dita-ot,robander/dita-ot,Hasimir/dita-ot