This rule is triggered on any lines that end with unexpected whitespace. To fix
this, remove the trailing space from the end of the line.

Note: Trailing space is allowed in indented and fenced code blocks because some
languages require it.

The `br_spaces` parameter allows an exception to this rule for a specific number
of trailing spaces, typically used to insert an explicit line break. The default
value allows 2 spaces to indicate a hard break (\<br> element).

Note: You must set `br_spaces` to a value >= 2 for this parameter to take
effect. Setting `br_spaces` to 1 behaves the same as 0, disallowing any trailing
spaces.

By default, this rule will not trigger when the allowed number of spaces is
used, even when it doesn't create a hard break (for example, at the end of a
paragraph). To report such instances as well, set the `strict` parameter to
`true`.

```markdown
Text text text
text[2 spaces]
```

Using spaces to indent blank lines inside a list item is usually not necessary,
but some parsers require it. Set the `list_item_empty_lines` parameter to `true`
to allow this (even when `strict` is `true`):

```markdown
- list item text
  [2 spaces]
  list item text
```

Rationale: Except when being used to create a line break, trailing whitespace
has no purpose and does not affect the rendering of content.