DOCS-716: SQL statement description template (#12673)

* CLICKHOUSEDOCS-716: Added the template for SQL-statement description.

* Update docs/_description_templates/template-statement.md
Co-authored-by: NIvan Blinkov <github@blinkov.ru>

* Update docs/_description_templates/template-statement.md
Co-authored-by: NIvan Blinkov <github@blinkov.ru>

* CLICKHOUSEDOCS-716: Updated by comments.
Co-authored-by: NSergei Shtykov <bayonet@yandex-team.ru>
Co-authored-by: Nemironyuk <em@don.ru>
Co-authored-by: NIvan Blinkov <github@blinkov.ru>

docs/_description_templates/template-statement.md

+# Statement name (for example, SHOW USER)
+
+Brief description of what the statement does.
+
+Syntax:
+
+```sql
+Syntax of the statement.
+```
+
+## Other necessary sections of the description (Optional)
+
+Examples of descriptions with a complicated structure:
+
+- https://clickhouse.tech/docs/en/sql-reference/statements/grant/
+- https://clickhouse.tech/docs/en/sql-reference/statements/revoke/
+- https://clickhouse.tech/docs/en/sql-reference/statements/select/join/
+
+
+## See Also (Optional)
+
+Links to related topics as a list.
+
+-   [link](#)