Click-extra

- Allow `color_option`, `command`, `config_option`, `extra_command`, `extra_group`, `group`, `help_option`, `show_params_option`, `table_format_option`, `timer_option`, `verbosity_option` and `version_option` decorators to be used without parenthesis.
- Fix wrapping of Cloup decorators by `extra_group`/`extra_command` decorators. Closes {issue}`489`.
- Add main dependency on `furo` which is referenced in ANSI-aware Pygment styles.
- Move all documentation assets to `assets` subfolder.

- Let `--version` option output system details when run on `python >= 3.10`.

- Fix overlapping detection of `linux` and `wsl2` platforms.
- Renders platform groups in documentation in Mermaid format instead of Graphviz. Add new dependency on `sphinxcontrib-mermaid`, removed dependency on `graphviz`.
- Produce dependency graph in Mermaid instead of Graphviz.

- Code, comments and documentation style change to conform to new QA workflows based on `ruff`.

- Rename `click_extra.platform` to `click_extra.platforms`.
- Refactor platforms and their groups with dataclasses instead of string IDs.
- Add new `LINUX_LAYERS`, `ALL_WINDOWS`, `BSD_WITHOUT_MACOS`, `EXTRA_GROUPS` and `ALL_GROUPS` groups.
- Add new dependency on `graphviz`.
- Activate Graphviz extension in Sphinx.
- Let Sphinx produce the dependency graph from Graphviz file.
- Produce platform graph dynamically.
- Rename `docs.py` to `docs_update.py` and allow this module to be called directly.

- Add support for new ANSI-capable lexers: `ansi-gap-console` and `ansi-gap-repl`.
- Auto-update table of supported lexers in documentation.
- Add test to search in Pygments' test data for REPL/terminal-like lexers, as candidates for ANSI-coloring.
- Depends on `importlib_metadata` for `Python < 3.8`.