docs: separate template syntax into multiple docs (#36954)

This is part of a re-factor of template syntax and
structure. The first phase breaks out template syntax
into multiple documents. The second phase will be
a rewrite of each doc.

Specifically, this PR does the following:

- Breaks sections of the current template syntax document each into their own page.
- Corrects the links to and from these new pages.
- Adds template syntax subsection to the left side NAV which contains all the new pages.
- Adds the new files to pullapprove.

PR Close #36954

aio/content/guide/router-tutorial-toh.md

@@ -1170,7 +1170,7 @@ The `ActivatedRoute.paramMap` property is an `Observable` map of route parameter
 The `paramMap` emits a new map of values that includes `id` when the user navigates to the component.
 In `ngOnInit()` you subscribe to those values, set the `selectedId`, and get the heroes.
 
-Update the template with a [class binding](guide/template-syntax#class-binding).
+Update the template with a [class binding](guide/attribute-binding#class-binding).
 The binding adds the `selected` CSS class when the comparison returns `true` and removes it when `false`.
 Look for it within the repeated `<li>` tag as shown here: