Separate markdown blocks ignote footnotes

[Cezar Tiv]

If markdown blocks have a footnote reference and footnote declaration in separate blocks, the editor doesn't link them as intended. It ignores the declaration and shows the reference as text.

Steps two reproduce:

1. Create 2 markdown blocks.
2. Top block has footnote reference:
   ¹
3. Bottom block has footnote declaration:

Footnotes

1. This is the footnote. ↩