Adding Page Constructor blocks inside the page

[martyanovandrey]

Description:
Enable the insertion of Page Constructor blocks directly into specific parts of markdown files. To achieve this, we should define and implement a syntax using directives.

Tasks:

1. Research and design the syntax for directives that can be used within MD files.
2. Implement the parsing logic to recognize and process these directives.
3. Allow the embedded Page Constructor blocks to render correctly within the MD content.
4. Update documentation to include guidance on using the new directive-based syntax.
5. Test the implementation to ensure compatibility with existing MD file structures.