update default values for docker image, add image for v15

Author: Anmol1696

starship/charts/devnet/defaults.yaml

@@ -794,7 +794,7 @@ defaultChains:
         coingecko_id: stake
         keywords: [ "stake" ]
   ethereum:
-    image: ghcr.io/hyperweb-io/starship/ethereum/client-go:latest
+    image: ghcr.io/hyperweb-io/starship/ethereum/client-go:v1.14.12
     home: /ethereum
     binary: geth
     prefix: eth

starship/docker/chains/versions.yaml

@@ -148,6 +148,7 @@ chains:
     tags:
       - latest
       - stable
+      - v1.15.0
       - v1.14.12
       - v1.14.11
   - name: prysm/beacon-chain