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

packages/core/src/metadata/directives.ts

@@ -684,7 +684,7 @@ export interface InputDecorator {
    * class App {}
    * ```
    *
-   * @see [Input and Output properties](guide/template-syntax#input-and-output-properties)
+   * @see [Input and Output properties](guide/inputs-outputs)
    */
   (bindingPropertyName?: string): any;
   new(bindingPropertyName?: string): any;
@@ -728,7 +728,7 @@ export interface OutputDecorator {
    *
    * See `Input` decorator for an example of providing a binding name.
    *
-   * @see [Input and Output properties](guide/template-syntax#input-and-output-properties)
+   * @see [Input and Output properties](guide/inputs-outputs)
    *
    */
   (bindingPropertyName?: string): any;