Spring Security Docs: Explain "namespace" before using it in reference guide

Summary

Chapter 8 of the current reference docs start using the term namespace without explaining its meaning in the given context first.

Actual Behavior

n/a

Expected Behavior

Give a short explanation (in brackets?) explaining its meaning in the given context (XML namespace? Spring Security?)...

Configuration

n/a

Version

5.2.0

Sample

n/a