Pandoc example:
.
Here is a footnote reference,[^1] and another.[^longnote]

[^1]: Here is the footnote.

[^longnote]: Here's one with multiple blocks.

    Subsequent paragraphs are indented to show that they
belong to the previous footnote.

        { some.code }

    The whole paragraph can be indented, or just the first
    line.  In this way, multi-paragraph footnotes work like
    multi-paragraph list items.

This paragraph won't be part of the note, because it
isn't indented.

This paragraph won't be part of the note neither, because it
isn't indented.
.
xxx
.


Duplicate footnotes:
.
[^xxxxx] [^xxxxx]

[^xxxxx]: foo
.
xxx
.



They could terminate each other:

.
[^1][^2][^3]

[^1]: foo
[^2]: bar
[^3]: baz
.
xxx
.


They could be inside blockquotes, and are lazy:
.
[^foo]

> [^foo]: bar
baz
.
xxx
.


Their labels could not contain spaces or newlines:

.
[^ foo]: bar baz

[^foo
]: bar baz
.
<p>[^ foo]: bar baz</p>
<p>[^foo
]: bar baz</p>
.


We support inline notes too (pandoc example):

.
Here is an inline note.^[Inlines notes are easier to write, since
you don't have to pick an identifier and move down to type the
note.]
.
xxx
.


They could have arbitrary markup:

.
foo^[ *bar* ]
.
xxx
.


Duplicate footnotes:
.
[^xxxxx] [^xxxxx]

[^xxxxx]: foo
.
xxx
.


Indents:

.
[^xxxxx] [^yyyyy]

[^xxxxx]: foo
    ---

[^yyyyy]: foo
   ---
.
xxx
.


Indents for the first line:

.
[^xxxxx] [^yyyyy]

[^xxxxx]:       foo

[^yyyyy]:        foo
.
xxx
.

Indents for the first line (tabs):
.
[^xxxxx]

[^xxxxx]:		foo
.
xxx
.


Security 1
.
[^__proto__]

[^__proto__]: blah
.
xxx
.


Security 2
.
[^hasOwnProperty]

[^hasOwnProperty]: blah
.
xxx
.


Should allow links in inline footnotes
.
Example^[this is another example https://github.com]
.
xxx
.


Should allow additional text in numeric footnote reference
.
Here is a footnote[^1] reference with [^2 added text].

[^1]: Here is a footnote.
[^2]: Here is another footnote.
.
xxx
.


Should allow additional text in long footnote reference
.
Here[^anote] is a footnote [^Bnote reference] with [^c-note added text].

[^anote]: Here is the first footnote.
[^Bnote]: Here is the second footnote.
[^c-note]: Here is the third footnote.
.
xxx
.


Regression test for #42
.
foo[^1] bar[^2].

[^1]:[^2]: baz
.
xxx
.