Use api3 as DOCKERHUB_USERNAME in docker-build CI workflow

Author: dcroote

.github/workflows/build-test.yml

@@ -102,7 +102,7 @@ jobs:
         run: yarn docker:scripts:npm-registry:stop
       - name: Publish Docker containers
         env:
-          DOCKERHUB_USERNAME: ${{ secrets.DOCKERHUB_USERNAME }}
+          DOCKERHUB_USERNAME: api3
           DOCKERHUB_TOKEN: ${{ secrets.DOCKERHUB_TOKEN }}
         run: yarn docker:scripts:docker:publish --dev --docker-tags ${{ github.sha }}
   unit-tests:

docker/README.md

@@ -273,7 +273,7 @@ Use the `--dev` option to push the images, with the `-dev` suffix in their name.
 
 You need to provide two environment variables to authenticate against the DockerHub registry:
 
-- `DOCKERHUB_USERNAME` - DockerHub username
+- `DOCKERHUB_USERNAME` - DockerHub username i.e. `api3`
 - `DOCKERHUB_TOKEN` - DockerHub access token
 
 Example: