Format first line of footnote definitions empty

[wooorm]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and couldn’t find anything (or linked relevant results below)

Problem

The first line of footnote definitions has some confusing properties:

For example, Mercury[^mercury], Venus[^venus], and Earth[^Earth].

[^Mercury]: **Mercury** is the first planet from the Sun and the smallest
     in the Solar System.

[^Venus]: > (block quote) **Venus** is the second planet from
    the Sun.

[^Earth]:         (does indented code work here?) **Earth** is the third planet
        from the Sun and the only astronomical object known to harbor life.

Yields:

For example, Mercury¹, Venus², and Earth³.

Solution

Format first line empty:

For example, Mercury[^mercury], Venus[^venus], and Earth[^Earth].

[^Mercury]:
    **Mercury** is the first planet from the Sun and the smallest
    in the Solar System.

[^Venus]:
    > (block quote) **Venus** is the second planet from
    > the Sun.

[^Earth]:
        (does indented code work here?) **Earth** is the third planet
        from the Sun and the only astronomical object known to harbor life.

Alternatives

.

Footnotes

1. Mercury is the first planet from the Sun and the smallest
   in the Solar System. ↩

2. (block quote) Venus is the second planet from
   the Sun.

   ↩

3. (does indented code work here?) Earth is the third planet
   from the Sun and the only astronomical object known to harbor life. ↩