docs: clarify deep linking requirements in REVIEW.md

Author: marcklingen

REVIEW.md

@@ -9,3 +9,4 @@ Please check the following:
 - When embedding videos from youtube, make sure to embed from `https://www.youtube-nocookie.com` instead of `https://www.youtube.com` to avoid cookies and tracking.
 - Use one H1 per markdown file, with subsections in order (`##`, `###`, etc.)—do not skip heading levels.
 - We never use `.gif` files, only `.mp4` files uploaded to `static.langfuse.com/docs-videos` to optimize for size and performance.
+- when deeplinking to a section via a link that uses the `#` anchor, make sure that this the anchor for this section is explicitly defined in the source page via `[#anchor]` at the end of the header line, e.g. `## Get Started [#get-started]`