Adding Toc for the "longish" spec pages.

[Seb]

On Friday, 29 December 2017 at 12:13:02 UTC, Mike Franklin wrote:
> On Friday, 29 December 2017 at 12:06:12 UTC, tipdbmp wrote:
>> It seems to me that some of the language reference/spec pages 
>> that are somewhat long,
>> could provide a Toc (Table of contents) which should help 
>> users see an overview of what's
>> there and improve the searchability and the navigation of the 
>> content.
>> The 'Functions' page has a Toc already.
>
> If you have a suggestion for improving the documentation, 
> please file an issue at https://issues.dlang.org/  Occasionally 
> contributors go fishing for easy issues like that in the issues 
> list and will submit pull requests.
>
> Even better, you may want to file a pull request yourself at 
> https://github.com/dlang/dlang.org
>
> Mike

Yes, opening an issue or PR is the best way to move things 
forward.
In this case, this is already on my radar and will happen soon 
(since a couple of weeks we already got a footer pagination). 
It's pretty ugly because Ddoc is used for dlang.org which makes 
trivial stuff like this rather complicated :/