Mirror of executablebooks/markdown-it-py#380 for
this repo.

- **`AGENTS.md`**: AI coding agent guide covering plugin architecture
(block/inline/core rule patterns), development commands (tox), code
style (Ruff/Mypy strict), fixture-based test patterns, and common
operations (adding plugins, rules, renderers)
- **`.github/workflows/copilot-setup-steps.yml`**: Copilot environment
setup — Python 3.11, uv, pre-commit, tox
- **`tox.ini`**: Added `pre-commit` and `mypy` tox environments so all
commands referenced in AGENTS.md are available; fixed docs builder
command to use `{posargs}` correctly (`tox -e docs-update -- linkcheck`
instead of `BUILDER=linkcheck`)

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: chrisjsewell <[email protected]>

Add a superscript plugin and associated tests ported from
<https://github.com/markdown-it/markdown-it-sup>.

Update documentation with superscript plugin and remove superscript (and
subscript, added in PR
<#122>) from list
of plugins to port.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Kyle King <[email protected]>
Co-authored-by: Chris Sewell <[email protected]>

## Summary

Adds two new plugins that require markdown-it-py >= 4.1.0:

### `gfm_autolink` — GFM autolink literals

Implements the [GFM autolinks
extension](https://github.github.com/gfm/#autolinks-extension-)
with three inline scanners:

- `www.` URLs (trigger char: `w`, via `add_terminator_char`)
- `http://`/`https://`/`mailto:`/`xmpp:` URLs (trigger char: `:`)
- Bare email addresses (trigger char: `@`)

Matching logic is ported from the Rust

[gfm_autolinks](https://github.com/markdown-it-rust/markdown-it-plugins.rs/tree/main/crates/gfm-autolinks)
crate. Covers GFM spec examples 622–635 plus additional edge cases
(trailing delimiters, emphasis integration, parentheses balancing,
etc.).

### `gfm` — Composite GFM plugin

A single-call plugin that enables a GFM-like configuration:

- Tables (built-in)
- Strikethrough with single and double tildes (built-in)
- GFM autolinks (`gfm_autolink`)
- Task lists (built-in)
- Alerts (built-in)
- Footnotes (`footnote_plugin`, inline=False)
- Dollar math (optional, disabled by default)
- Front matter (optional, disabled by default)

Tag filtering is noted as a TODO.

### Other changes

- `tox.ini`: test envs pin `markdown-it-py>=4.1.0`
- `pyproject.toml`: added `pytest-timeout` to testing extras

### References

- [GFM spec](https://github.github.com/gfm/)
- [GitHub basic formatting
syntax](https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax)
- markdown-it-py 4.1.0 `add_terminator_char` API (PR
executablebooks/markdown-it-py#391)