chore(changelog): show full commit message (#423)

This allows someone reading the changelog to search for information
about breaking changes or implementation of new functionality.

- refactored the commit template part to a macro instead of repeating it
- added a link to the commit and to the release
- updated the current changelog for the alpha and unreleased changes
- Automatically changed the existing * lists to - lists

.markdownlint.yaml

@@ -7,3 +7,6 @@ no-inline-html:
     - summary
 line-length:
   line_length: 100
+
+# to support repeated headers in the changelog
+no-duplicate-heading: false