Specification Style Guidelines have some outdated rules

In discussion during code review, some decisions have been pointed out that have not been codified in the guidelines:

1. The current rule for indentation in itemize doesn't seem accurate. That is:

   \begin{itemize}
   \item
     A B
     C D.
   \end{itemize}
   

   I have indented the library part of reflections like this, believing that the guidelines are correct, but I can see that Jens doesn't bother indenting after \item.

2. We have a rule to indent two spaces after a template-head, but this allegedly doesn't apply to struct. Some C++26 wording still follows this outdated rule, like:

   template<auto V>
     struct nontype_t {
       explicit nontype_t() = default;
     };
   template<auto V> constexpr nontype_t<V> nontype{};
   

   If this is not what we want, it should be clarified.

@burblebee do you have links to the discussions where these decisions have been made?

Start with the Specification Style Guidelines wiki page linked in the issue and locate the rules for itemize indentation and indentation after a template-head. Confirm the referenced code-review decisions, then update the guidelines so both examples have an explicit, agreed-upon rule.