Kapacitor release notes update - v1.6.3 (#3702)

* Kapacitor release notes update

* updated PigPanda and Alerta

* Added additonal detail from Emrys' feedback

Co-authored-by: kelseiv <47797004+kelseiv@users.noreply.github.com>

content/kapacitor/v1.6/about_the_project/releasenotes-changelog.md

@@ -7,6 +7,25 @@ menu:
     name: Release notes
 ---
 
+## v1.6.3 [2022-01-20]
+
+### Features
+
+- Add support for custom `attributes` field in [Alerta event handler](/kapacitor/v1.6/event_handlers/alerta/). 
+- Add `host` and `attribute` options to [BigPanda event handler](/kapacitor/v1.6/event_handlers/bigpanda/). 
+  - `host`: Corresponds to host alert payload parameter; identifies the main object that caused the alert.
+  - `attribute`: Option to add additional attribute(s) to the alert payload.
+- Add new `auto-attributes` configuration option to BigPanda node.
+-  Ability to add new headers to HTTP posts directly in `env var` config. 
+- `Topic queue length` is now configurable. This allows you to set a `topic-buffer-length` parameter in the Kapacitor config file in the
+[alert](https://docs.influxdata.com/kapacitor/v1.6/administration/configuration/#alert) section. The default is 5000.  Minimum length
+is 1000.
+- Add new `address template` to email alert. Email addresses no longer need to be hardcoded; can be derived directly from data.
+
+### Bug fixes
+- Deprecation in response to [sweet32](https://sweet32.info/): stopped using block ciphers.
+- Add additional detail to the error message `missing flux data`. This error is generated when issues occur when running a **Flux** query within a Batch TICKscript.
+
 ## v1.6.2 [2021-09-24]
 
 ### Features