3.0.0: Native Attributes; trail-less registration; generic sections from attributes

Replaces Doctrine annoations with native PHP attributes, removing the deprecated depenedency. Adds a new way of registering ShortcodeDocumentation-annotated classes without the need for an additional import. Adds the option of rendering generic sections into the DocumentationMenu with the DocumentationSection attribute annotation.

Breaking changes: https://github.com/gebruederheitz/wp-theme-docs?tab=readme-ov-file#v2-to-v3

• feat: Leave some space at the bottom of the page (4d71a5b)
• fix: Make parameters & examples optional for shortcode docs (54e53f9)
• docs: v3 migration & new features (033977f)
• fix: trait-less registration for static class methods (be8ff62)
• chore: Add demo / tests via wp theme & plugin for ddev (c3527e1)
• chore: Add ddev configuration (4c46087)
• feat: Better generic sections; trait-less init (d08d0eb)
• feat: Generic doc sections with optional markdown via attribute & trait (ac439a5)
• docs: Document breaking change & migration (693c6af)
• chore: Improved DX with local WP installation (f0f2920)
• feat: Replace doctrine annotations with native php attributes (req. >=8.0) (1480513)
• chore: Update tooling (ba538f4)