Vectorize: Make index naming requirement explicit (#22335)

Author: s-h-a-d-o-w

src/content/docs/vectorize/best-practices/create-indexes.mdx

@@ -11,7 +11,7 @@ Indexes are the "atom" of Vectorize. Vectors are inserted into an index and enab
 
 Creating an index requires three inputs:
 
-- A name, for example `prod-search-index` or `recommendations-idx-dev`.
+- A kebab-cased name, such as `prod-search-index` or `recommendations-idx-dev`.
 - The (fixed) [dimension size](#dimensions) of each vector, for example 384 or 1536.
 - The (fixed) [distance metric](#distance-metrics) to use for calculating vector similarity.