Add shared to list of available substitution sources in _templates.…

…md (#7777)

* Update _templates.md

- Added "shared" substitution variable to documentation
- Fixed formatting issue

* Adjust for consistency with request transformer advanced

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Co-authored-by: lena-larionova <[email protected]>

app/_hub/kong-inc/request-transformer/how-to/_templates.md

@@ -9,10 +9,11 @@ You can use any of the current request headers, query parameters, and captured U
 groups as templates to populate supported configuration fields.
 
 | Request Parameter | Template
-| ------------- | -----------
-| header        | `$(headers.<header_name>)`, `$(headers["<Header-Name>"])` or `$(headers["<header-name>"])`)
-| querystring   | `$(query_params.<query-param-name>)` or `$(query_params["<query-param-name>"])`)
-| captured URIs | `$(uri_captures.<group-name>)` or `$(uri_captures["<group-name>"])`)
+| -------------- | -----------
+| header         | `$(headers.<header_name>)`, `$(headers["<Header-Name>"])` or `$(headers["<header-name>"])`
+| querystring    | `$(query_params.<query-param-name>)` or `$(query_params["<query-param-name>"])`
+| captured URIs  | `$(uri_captures.<group-name>)` or `$(uri_captures["<group-name>"])`
+| shared variables | `$(shared.<variable-name>)` or `$(shared["<variable-name>"])`)
 
 To escape a template, wrap it inside quotes and pass inside another template.
 For example: