Support of set typst root or take env TYPST_ROOT #159

Rheo don't seem to support set --root for typst or take env variable to set root level

Thanks to make typst awsome i have a solo repo with this architechture

exports/book1/pdf
exports/book1/epub
exports/book1/html

texts/book1/book1.typ
texts/book2/book2.typ

theme/uniontheme.typ
theme/covers/covers.svg

And i use a lot the typst root parameter , i cannot make its works with rheo

I have to move all my theme to a differents folder to use rheo
did you think its something rheo would support ( typst already support it so maybe its just env to be pass to rheo)

On top on my texts/book1/book1.typ i got

#import "../../theme/uniontheme.typ": *

I got this error
Error: Compilation { count: 1, errors: "path \"../../theme/uniontheme.typ\" would escape the project root" }

= hint: cannot access files outside of the project sandbox
= hint: you can adjust the project root with the --root argument