Define blocks for easy overriding of the page rendering

[Aeliot-Tm]

Q	A
Bug fix?	no
New feature?	yes
BC breaks?	no
Deprecations?	no
Tests pass?	yes
Documented?	yes
License	MIT

There are added new blocks for easy overriding of the page rendering.
It is useful then you want to add new fields on the page.

For example, for handling of API assess tokens.

Additionally:

• Docs moved from the src/Resouces/doc directory to docs in the repository root.
• Fixed links to them in README.md.
• Restored docs which was removed by chance before.

[Aeliot-Tm]

May be it has sense to create a set of templates for common solutions?

[Aeliot-Tm]

@mcg-web Could you check it, please

[Aeliot-Tm]

Added template @OverblogGraphiQL/GraphiQL/auth.html.twig providing two common authentication ways.

How it looks like:

There is:

1. Header used for the authorization.
2. Header value (token) for the authorization.
3. Button to load schema when the header value (token) typed.

[Aeliot-Tm]

@ruudk @mcg-web Could you check it, please?

[mcg-web]

Thank you and sorry for the late reply!