Document MongoDB query and update operators that can be used in-game

[tukib]

Problem

Currently, we reference the official MongoDB docs for query and update operators. But, not all of these are available in-game, and there is no explicit documentation to help with this.

• E.g. from #db.f(..): "Various MongoDB query operators can be used"

Context

This has been brought up a few times by new players.

To solve:

• Add Query Operators and Update Operators pages to https://wiki.hackmud.com/scripting/db
  • E.g. A table of valid operations and brief descriptions
• Reference these on the #db directive pages.
• Reference these on the relevant trust script pages (e.g. market.browse and sys.upgrades)

[Fayti1703]

We could grab the valid operators from the old versions of the MongoDB docs -- they're still available on the docs page, though only as a .tar.gz file download?