Adding explaination to release docs (#1696)

doc/developer/tooling.rst

@@ -116,7 +116,8 @@ minor PRs won't require a release note.
 In particular, in the release notes, you will find four sections in the releasee notes:
 
 1. **New Features** - A new feature (or major addition to a current feature) was added to the code.
-2. **API Changes** - ANY change to the public-facing API of ARMI.
+2. **API Changes** - ANY breaking change to the public-facing API of ARMI. (A breaking change is
+   when you change the existing API, not when you add something new to the API.)
 3. **Bug Fixes** - ANY bug fix in the code (not the documentation), no matter how minor.
 4. **Changes that Affect Requirements** - If you touch the code (``impl``) or test (``test``) for
    anything that currently has a requirement crumb. (This must be a non-trivial change.)

doc/release/0.3.rst

@@ -8,8 +8,8 @@ Release Date: TBD
 
 New Features
 ------------
-#. Conserve mass by component in assembly.setBlockMesh(). (`PR#1665 <https://github.com/terrapower/armi/pull/1665>`_)
-#. Removal of the Block.reactor property. (`PR#1425 <https://github.com/terrapower/armi/pull/1425>`_)
+#. Conserve mass by component in ``assembly.setBlockMesh()``. (`PR#1665 <https://github.com/terrapower/armi/pull/1665>`_)
+#. Removal of the ``Block.reactor`` property. (`PR#1425 <https://github.com/terrapower/armi/pull/1425>`_)
 #. System information is now also logged on Linux. (`PR#1689 <https://github.com/terrapower/armi/pull/1689>`_)
 #. TBD