Has your company had a test strategy document before?
Do you know what your company is expecting when they ask for a “test strategy document”?
You might have a fair bit of freedom to define what YOU think would benefit the company best when it comes to a company-wide test strategy, feel free to pick and choose what ISTQB suggests, but honestly I think it’s up to you to focus on the aspects that will best benefit your company.
(I created one for my company a few months ago that also is working with Agile, and focussed a lot on making sure testers get involved early and having clear communication be an integral part of our test strategy).
Lastly, the hard work comes not in creating the document but in the follow-up making sure people follow it, understand it etc.