Markdown uses email conventions for quoting blocks of text.

> This is a block quote. This paragraph has two lines.
>
> 1. This is a list inside a block quote.
> 2. Second item.

A "lazy" form, which requires the `>` character only on the first line of each
block, is also allowed:

> This is a block quote. This paragraph has two lines.

> 1. This is a list inside a block quote.
> 2. Second item.

Among the block elements that can be contained in a block quote are other block
quotes. That is, block quotes can be nested:

> This is a block quote.
>
> > A block quote within a block quote.

If the `>` character is followed by an optional space, that space will be
considered part of the block quote marker and not part of the indentation of the
contents. Thus, to put an indented code block in a block quote, you need five
spaces after the `>`:

> ```
> code
> ```

### Extension: `blank_before_blockquote`

Original Markdown syntax does not require a blank line before a block quote.
Pandoc does require this (except, of course, at the beginning of the document).
The reason for the requirement is that it is all too easy for a `>` to end up at
the beginning of a line by accident (perhaps through line wrapping). So, unless
the `markdown_strict` format is used, the following does not produce a nested
block quote in pandoc:

> This is a block quote. > Not nested, since `blank_before_blockquote` is
> enabled by default

> practical skills in:
>
> - Developing and integrating custom formats to support diverse outputs while
>   reducing repetition across projects.
> - Substituting Quarto’s templates with your own to customize formats beyond
>   the built-in options.
> - Implementing filters to automate and streamline content transformation.
