[remark-lint-list-item-style] Does not properly check first letter of bold, italic, and struck-through list items

[Xunnamius]

The problem

Seems like the first character of bold, italic, struck-through, etc list items are not being chosen properly during the capitalization check.

Reproduction steps

Triggers a warning:

_Is compiling and not patching:_

- `build-tool ‑patch=false`
- `build-tool ‑no‑patch`
- _`build-tool ‑no‑patch ‑no‑only‑patch`_ (this is the interesting one)

Expected behavior

Should not trigger a warning:

_Is compiling and not patching:_

- `build-tool ‑patch=false`
- `build-tool ‑no‑patch`
- _`build-tool ‑no‑patch ‑no‑only‑patch`_ (this is the interesting one)