How to add App block on page programmatically when app just installed?

[prudenko]

I am developing a Shopify app with a theme-app extension. 
As a final result after installation, I want to add a custom page with app block from the theme-app extension in the online store.
I found how to create a page with Page API, but I can not find a programmatic way to add app block on this page. 

[Sh1Ft]

I would also be interested to know if it's possible. I see multiple apps in the App Store, that for example change the way your product page looks, after you install it, without any additional user interaction. I couldn't find anything like that in Shopify documentation.

[RohitGohel]

Hello Prudenko,

Have you got any solution for that issue, because I am facing the same issue.