Add information about the docker build changes in the release notes

Author: na--

release notes/v0.23.0.md

@@ -1,6 +1,8 @@
 v0.23.0 is here! :tada:
 
-Hopefully this is the last intermediary release before v1.0.0. It is a bit light on new features, but it includes a lot of bug fixes and minor improvements! Thanks to @sherrman, @ofauchon, @AndriiChuzhynov, @entone, @mariolopjr, and @tkbky for contributing to this release!
+Hopefully this is the last intermediary release before v1.0.0. It is a bit light on new features, but it includes a lot of bug fixes and minor improvements! Also, the `latest` Docker tag will point to this release until we release the next stable one. Users wanting to use the bleeding edge k6 features can do that via the new `master` docker tag, which is pushed by every CI build of the git `master` branch.
+
+Thanks to @sherrman, @ofauchon, @AndriiChuzhynov, @entone, @mariolopjr, and @tkbky for contributing to this release!
 
 To see what's left for the v1.0.0 release, check out [this milestone](https://github.com/loadimpact/k6/milestone/4)!
 
@@ -112,7 +114,8 @@ You can now specify the minimum amount of time a single iteration should take vi
 * Cloud output: improved outlier metric detection for small batches. (#744)
 * Use 20 as the the default values of the `batch` and `batchPerHost` options. They determine the maximum number of parallel requests (in total and per-host respectively) an `http.batch()` call will make per VU. The previous value for `batch` was 10 and for `batchPerHost` it was 0 (unlimited). We now also use their values to determine the maximum number of open idle connections in a VU. (#685)
 * Due to refactoring needed for the redirect fixes, the NTLM authentication library k6 uses is changed from [this](https://github.com/ThomsonReutersEikon/go-ntlm/) to [this](https://github.com/Azure/go-ntlmssp). (#753)
-* Switched the default CircleCI tests and linting to use Go 1.11.1, but we still maintain 1.10 compatibility by running all of the tests with Go 1.10.3 too. Official k6 standalone builds will also be done with Go 1.11+ from now on. (#813)
+* Switched the default CircleCI tests and linting to use Go 1.11.2, but we still maintain 1.10 compatibility by running all of the tests with Go 1.10.3 too. Official k6 standalone builds will also be done with Go 1.11+ from now on. (#813)
+* Automated docker builds of the git `master` branch will now tag the resulting docker image as `master` as well. The `latest` docker tag will point to the latest stable official release, so it will be equivalent to `v0.23.0` until we release the next k6 version. (#846)
 
 ## Bugs fixed!