ci: tag latest on every push to main (#25)

Amp-Thread-ID: https://ampcode.com/threads/T-019c6c7d-918e-734a-9450-4e8d663df93b

Co-authored-by: Amp <amp@ampcode.com>

Author: emmajam

.github/workflows/release.yml

@@ -57,6 +57,7 @@ jobs:
           platforms: linux/amd64
           push: true
           tags: |
+            ghcr.io/tempoxyz/rpc-tester:latest
             ghcr.io/tempoxyz/rpc-tester:${{ steps.vars.outputs.sha_short }}
           cache-from: type=gha
           cache-to: type=gha,mode=max