[1.0.0-alpha2] Skip region--content.html.twig

Problem/Motivation

This module is already in a advanced state:

• ✅ page.html.twig and info.yml's regions are skipped
• ✅ At module activation, all blocks are automatically put in the page layout root slot

However, instead of building the page variable or html.html.twig, we are building the content variable of region--content.html.twig (or region.html.twig)

content is a mandatory region in theme systems.

Proposed resolution

Find a way of skipping all page regions, because display builder take control of this layer.

Also, do we remove this part from README.md? Because keeping the blocks looks OK

Disable ALL blocks from block layout page (/admin/structure/block) and KEEP only: Help and Main page content