[Bug] Markdown parser fails to parse metadata links section with , character in the link

[dvorka]

Bug description:

Markdown parser fails to parse metadata links section with , character in the link.

Repro:

# Outline Name <!-- Metadata: links: [root link](./a,b.pdf); -->

O text.

Hints:

• Links must support \ escaping, but in the way which will not slow down the parsing.