I've had to edit typst recently and I used
https://codeberg.org/meow_king/typst-ts-mode
And the LSP: https://github.com/Myriad-Dreamin/tinymist
Specifically for doom, you'd add typst-ts-mode in your packages.el in a package! entry and check either eglot or lsp-mode doc for how to configure the LSP.
On average, electrons "move forward" much much slower than that:
https://en.wikipedia.org/wiki/Drift_velocity
But even the whole "electrical signal" is slower than the speed of light:
https://en.wikipedia.org/wiki/Velocity_factor#Typical_velocity_factors