Is there any way I can check script syntax without using RouterOS or any Mikrotik device? Any library or cli application? Or maybe something like docker image of RouterOS?

I think non-RouterOS rsc script interpreter doesn't exists, there are syntax highlighting plugins/extensions for some text editors/ide (notepad++, sublime text, vsc) but highlighting can't guarantee if syntax is accurate. You can use CHR on VirtualBox as free solution for this.