fix(plugins/links): mark link_open as reflink

[moki]

plugins/links

We have reflink syntax, this markup [{#T}](file.md) extracts title from file.md and uses it as link text.

We need to mark link_open token with markup: reflink(analogous to how autolinks are parsed).

Right now i am doing it inside @diplodoc-platform/markdown-translation library when rendering tokens into XML.

Objectively links of reflink type should just be marked as such by parser.

to easier understand the token structure checkout tokens tab: link to the playground