[Feature Request] Please add negative relative dates.

[imesha10]

Problem

Hello, currently there is support for relative dates but not negative relative dates. Sometimes I have an event to start 1 or 2 days before the previous event and continue forward a specified amount of time. Please add support to this or let me know if this is already something that can be done. I have read the documentation and didn't find anything regarding this.

Possible notation example:

group TestGroup:
2023-05-06/1 week: test item 1
-1 day/1 week: test item 2
endGroup

One more thing...

I use the vscode extension, if it's possible is there a way for me to manually update the parser?