magento/devdocs#: Set page layout type

[atwixfirster]

Purpose of this pull request

This pull request (PR) extends Page layout > Page layouts declaration section. It adds information how developer can change page layout type.

Affected DevDocs pages

• https://devdocs.magento.com/guides/v2.1/frontend-dev-guide/layouts/layout-types.html
• https://devdocs.magento.com/guides/v2.2/frontend-dev-guide/layouts/layout-types.html
• https://devdocs.magento.com/guides/v2.3/frontend-dev-guide/layouts/layout-types.html

Links to Magento source code

• https://github.com/magento/magento2/blob/2.3.1/app/code/Magento/Theme/view/base/layouts.xml
• https://github.com/magento/magento2/blob/2.3.1/app/code/Magento/Theme/view/frontend/layouts.xml
• https://github.com/magento/magento2/blob/2.3.1/app/code/Magento/Theme/view/adminhtml/layouts.xml

whatsnew
Added information about page layout types and a new code example that shows how to use them

[devops-devdocs]

An admin must run tests on this PR before it can be merged.

[ronak2ram]

Hi @atwixfirster
Thanks for your contributions. This PR is very helpful to the developer for understanding the Page layout.

[atwixfirster]

Hi @atwixfirster
Thanks for your contributions. This PR is very helpful to the developer for understanding the Page layout.

Thanks for approve, @ronak2ram !

With my pleasure 😊

[jeff-matthews]

Please accept the suggested edits

[jeff-matthews]

Thanks @atwixfirster!

[jeff-matthews]

running tests

[jeff-matthews]

Tests failed. Here's the log:

+ rake test:cicd
�[35mChecking links with htmlproofer...�[0m
Running ["LinkChecker::DoubleSlashCheck", "ImageCheck", "LinkCheck", "ScriptCheck"] on ["_site"] on *.html... 

Ran on 4105 files!

- internal image /guides/v2.1/frontend-dev-guide/images/version.png does not exist
  *  _site/guides/v2.1/frontend-dev-guide/layouts/layout-types.html (line 315)
- internal image /guides/v2.2/frontend-dev-guide/images/version.png does not exist
  *  _site/guides/v2.2/frontend-dev-guide/layouts/layout-types.html (line 315)
- internal image /guides/v2.3/frontend-dev-guide/images/version.png does not exist
  *  _site/guides/v2.3/frontend-dev-guide/layouts/layout-types.html (line 315)
rake aborted!
HTML-Proofer found 3 failures!```

[jeff-matthews]

running tests

[ghost]

Hi @atwixfirster, thank you for your contribution!
Please, complete Contribution Survey, it will take less than a minute.
Your feedback will help us to improve contribution process.