refactor(hooks): replace cz-conventional-changelog with cz-commitlint

This change replaces cz-conventional-changelog with cz-commitlint, which
automatically configures Commitizen using our commitlint configuration
file. Currently, we use some manual Javascript magic to load our
Commitizen configuration into commitlint (the opposite of what's
introduced by this change), which can be removed.

With this change, we also move our commitlint configuration into a
new `changelog.yaml` file. This file holds the same data as `.cz.json`
previously did.

Change-Id: I14ff2308f1a0b2b293c2128b28ca2df578ce9c1c
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/docs/process/commit-style.rst b/docs/process/commit-style.rst
index e9df5ce..de899ab 100644
--- a/docs/process/commit-style.rst
+++ b/docs/process/commit-style.rst
@@ -79,11 +79,10 @@
 +--------------+---------------------------------------------------------------+
 
 The permissible `scopes` are more flexible, and we maintain a list of them in
-our :download:`Commitizen configuration file <../../.cz.json>`. Scopes in this
-file are organized by their changelog section, each of which may have one or
-more accepted scopes, but only the first of which is considered to be "blessed".
-Scopes that are not blessed exist for changes submitted before scope enforcement
-came into effect, and are considered deprecated.
+our :download:`changelog configuration file <../../changelog.yaml>`. Scopes in
+this file are organized by their changelog section, where each changelog section
+has a single scope that is considered to be blessed, and possibly several
+deprecated scopes. Please avoid using deprecated scopes.
 
 While we don't enforce scopes strictly, we do ask that commits use these if they
 can, or add their own if no appropriate one exists (see :ref:`Adding Scopes`).