chore(ci): Automatically update CHANGELOG upon release

Author: efcasado

.releaserc

@@ -28,6 +28,11 @@
         ["@semantic-release/exec", {
             "prepareCmd": "mv dist efcasado-splunk-datasource; tar -czvf efcasado-splunk-datasource-${nextRelease.version}.tar.gz efcasado-splunk-datasource"
         }],
+        ["@semantic-release/git",
+         {
+             "assets": ["CHANGELOG.md"]
+         }
+        ],
         ["@semantic-release/github",
          {
              "assets": ["efcasado-splunk-datasource-*.tar.gz"]