Standardize syntax

Logseq takes advantage of Markdown as an universal standard but when adding features it introduces arbitrary syntax and this could reduce interoperability with other PKMS.

I think it’s time to standardize these extensions to Markdown, for example #hashtags, [[wikilinks]] and queries.

Please take inspiration from something like Matrix Spec Change Proposals, Python Enhancement Proposals, W3C standards, XMPP Extension Protocols etc.

Maybe make it Logseq-agnostic and involve other PKMS like Obsidian.