Feature/base on html5 elements refactor

[vardumper]

Please ignore everything PHP (especially in src/ folder). It just helps me auto-generate files. Everything PHP will not be in the final PR - unless useful.

This pull request updates the composer.json file to add Composer package management support for the project. The most important changes include specifying a new dependency and configuring autoloading for the source code.

Composer integration and configuration:

• Added a require section to include the vardumper/extended-htmldocument package as a dependency.
• Added an autoload section using PSR-4 to map the PicoCss\Pico namespace to the src/ directory.

[vardumper]

The idea is to move styles into HTML element scss files. The benefit I want to have is having to learn less PicoCSS SCSS "madness", but being able to write themes by allowing me to work with the well-known HTML elements' scss, rather than modules.
Using a postcss plugin, it should be possible to merge duplicate css rules back into the current pico.css format.

Once I modify src/Resources/picocss.yaml, I run php bin/console merge:specs. This gives me an updated HTML5 specification file (src/Resources/picocss-html5-specification.yaml).

Then I run vendor/bin/ext-html make:all --specification=src/Resources/picocss-html5-specification.yaml which updates all Html\Element\Classes and all Html\Enum\Classes.

Finally I run php bin/console make:sass which is creating new scss/inline|block folders and add more scss files.

Basically, the only things I want to actually really manually refactor here are content forms folders - these I want to replace with the new inline/block folders. void elements are intentionally left out due to not being visible.