update changelog and dev notes (#58)

CHANGELOG.md

@@ -5,7 +5,7 @@
 
 - support handlers being registered for (task definition) types (#58 BREAKING CHANGE)
 
-### Migration notes for breaking changes
+## Migration notes for breaking changes
 
 - replace ```AddTaskHandler("id", handlerFunc)``` with ```NewTaskHandler.Id("id").Handler(handlerFunc)```
 

DEVELOPMENT.md

@@ -16,11 +16,16 @@ The documentation on Github pages is build via [MkDocs](https://www.mkdocs.org/)
 
 1. ensure you have a Python 3.8+ environment installed
 2. install MkDocs, according to their https://www.mkdocs.org/user-guide/installation/
+    * shortcut: ```pip3 install -r doc-requirements.txt```
 3. within this source repo, run ```mkdocs build``` to get a version of the HTML files
 
-Alternatively, you could use ```mkdocs serve``` to have a local test-server running,
+Alternatively, you could use a local test-server,
 which eases the manual validation/verification of documentation updates. 
 
+```shell
+mkdocs serve
+```
+
 #### automated Github Pages update
 
 There's a Github Action [update-gh-pages.yaml](./.github/workflows/update-gh-pages.yml),