docs(CHANGES): Note mypy strict compliance

Author: tony

CHANGES

@@ -25,6 +25,12 @@ $ pipx install --suffix=@next 'tmuxp' --pip-args '\--pre' --force
 
 ### Development
 
+- **Improved typings**
+
+  Now [`mypy --strict`] compliant (#859)
+
+  [`mypy --strict`]: https://mypy.readthedocs.io/en/stable/command_line.html#cmdoption-mypy-strict
+
 - Poetry 1.5.1 -> 1.6.1 (#885)
 
 ## tmuxp 1.30.1 (2023-09-09)
@@ -35,7 +41,7 @@ _Maintenance only, no bug fixes or new features_
 
 - Cut last python 3.7 release (EOL was June 27th, 2023)
 
-  For security updates, a 1.30.x branch can be maintained for a limited time, 
+  For security updates, a 1.30.x branch can be maintained for a limited time,
   if necessary.
 
 ## tmuxp 1.30.0 (2023-09-04)
@@ -49,6 +55,7 @@ _Maintenance only, no bug fixes or new features_
   This includes fixes made by hand alongside ruff's automated fixes. The more
   stringent rules include import sorting, and still runs almost instantly
   against the whole codebase.
+
 - CI: `black . --check` now runs on pushes and pull requests
 
 ### Packaging