Add support for multi-paragraph footnotes

[andreubotella]

Describe the bug

dprint-plugin-markdown version: 0.15.2

Input Code

Some paragraph with a footnote[^1].

[^1]: Footnotes, as well as endnotes, are strings of text placed at the bottom
of a page in a book or document or at the end of a chapter, volume, or the whole
text.

    The footnote can provide an author's comments on the main text or
[citations](https://en.wikipedia.org/wiki/Citation) of a reference work in
support of the text.

With markdown-it-footnote, this parses as a paragraph followed by a single footnote containing two paragraphs:

Expected Output

No change, presumably.

Actual Output

Some paragraph with a footnote[^1].

[^1]: Footnotes, as well as endnotes, are strings of text placed at the bottom
of a page in a book or document or at the end of a chapter, volume, or the whole
text.

    The footnote can provide an author's comments on the main text or

[citations](https://en.wikipedia.org/wiki/Citation) of a reference work in
support of the text.