feat(accordion): add accordion component main behaviors

[pixu1980]

• handles only <details> element children
• if <details> child is a "wcag-details" the "wcag-details.toggle" event is handled and a "wcag-accordion.toggle" is emitted
• name attribute is watched and updates all the name attributes of <details> children
• name can be updated/read with public setter/getter
• a mutation observer watches for attribute changes and for childList changes, updating every <details> child with the proper name attribute
• is the name attribute is not present, there's a {{UUID}}-accordion fallback