taskc 0.1.0

Scan markdown task markers and generate a beautiful static task catalog page.
Documentation
# Manual Test Instructions

To test against this fixture specifically:

```sh
cd examples/manual-e2e-fixture
cargo run --manifest-path ../../Cargo.toml --
```

Expected results:
- `tasks.html` is created in `examples/manual-e2e-fixture/`.
- Summary says `Generated 3 tasks from 4 markdown files`.
- Task cards are collapsed by default (titles visible, bodies hidden).
- `Expand all` button opens every task; pressing again collapses all.
- Dark mode is default; `Light mode` button switches theme and back.
- Includes task titles:
  - `Root task: onboarding`
  - `App task: release checklist`
  - `Docs task: write guide`
- Excludes titles from ignored directories:
  - `Ignored node_modules task`
  - `Ignored target task`
  - `Ignored hidden task`