FR: Add `@callout` as a queryable object

[jeetsukumaran]

It would be very nice if @callout blocks could also be surfaced as data objects.

Proposed fields for @callout:

• type: The callout type (e.g., info, warning, tip, etc.)
• title: If the callout has an explicit title
• body: The full inner content of the callout
• tags: Any recognized tags inside the callout (optional, if applicable)

Benefits:

• Allows users to treat callouts as structured data.
• Makes it easier to gather notes, warnings, tips, and other block-level content into dashboards or reports.

A personal use-case for me is quotations,e.g.

> [!quotation] "The most valuable statement in science"
>
> > The most elementary and valuable statement in science, the beginning of wisdom, is: "I do not know."
>
> — [Commander Data ()](https://en.wikipedia.org/wiki/Data_(Star_Trek)) [Star Trek: The Next Generation Season 2, Episode 2: Where Silence Has Lease](https://memory-alpha.fandom.com/wiki/Where_Silence_Has_Lease_(episode))

> [!quotation]
> 
> > The epistemological value of probability theory is based on the fact that chance phenomena, considered collectively and on a grand scale, create non-random regularity.
> 
> — (Kolmogorov, 1954): Limit Distributions for Sums of Independent Random Variables

I have these scattered throughout the vault, usually in literature notes or manuscript notes. Nice to see them all in a table.

const info = dc.useQuery("@callout and type='info'");
const quotes = dc.useQuery("@callout and type='quotation'" and title=''");

Can also conceive of using todo, bug, important etc. callouts for productivity. Lots of flexibility in representing information, including both external and internal links, unlike frontmatter.

[blacksmithgu]

This seems reasonable.

[William-A-A]

Also : if "sub" elements to callouts are comming back, Like Sections, and list-items, tasks etc. That would be AMAZING ! Right now, even with a "list-item" query, lists item from callouts are not returning.