Update texmate grammar with more accurate representation of the new syntax

[tothambrus11]

The language definition file is available here as json: https://github.com/hylo-lang/vscode-hylo/blob/main/syntaxes/hylo.tmLanguage.json

We should update this file to more closely correspond with the new frontend's syntax.

[tothambrus11]

See also update syntax specification according to new frontend