[jlreq] new commits pushed by frivoal

The following commits were just pushed by frivoal to https://github.com/w3c/jlreq:

* Add clarification to the introduction (#204)

This leaves room for future extensions, manual overrides, and other
tweaks, while letting the document focus on the simple system without
getting into all sorts of corner cases and side discussions.

Closes #200
  by Florian Rivoal
https://github.com/w3c/jlreq/commit/ef8bc680c3a2de9ed0f0814f597b5d4fb757243a