Update 1.21.0 (#4)

* Read TESLAMATE_TAG from build.json

* Update 1.21.0

* Remove PR trigger

* Update changelog

.github/workflows/teslamate.yml

@@ -7,20 +7,12 @@ on:
     paths:
       - '**'
       - '!**.md'
-  pull_request:
-    branches:
-      - main
-    paths:
-      - '**'
-      - '!**.md'
 
 env:
   DOCKER_USERNAME: mattffffff
 
 jobs:
   build:
-    env:
-      TESLAMATE_TAG: 1.20.1
 
     runs-on: ubuntu-latest
 
@@ -33,6 +25,9 @@ jobs:
     - uses: actions/checkout@v2
       with:
         submodules: 'true'
+    - name: Set TESLAMATE_TAG
+      run: |
+        echo "TESLAMATE_TAG=$(jq -r '.args.TESLAMATE_TAG ' < build.json)" >> $GITHUB_ENV
     - name: Docker version
       run: docker version
     - name: Setup qemu