chore: configure linters and fix renovate post-upgrade commands

- Add yamllint indentation rule to enforce 2 spaces
- Add allowedPostUpgradeCommands to renovate config to permit sync-template-version.sh script

Fixes #1279

.yamllint

@@ -2,6 +2,9 @@
 extends: default
 
 rules:
+  indentation:
+    spaces: 2
+    indent-sequences: true
   line-length:
     max: 160
     level: warning

renovate.json

@@ -160,6 +160,9 @@
       "datasourceTemplate": "terraform-provider"
     }
   ],
+  "allowedPostUpgradeCommands": [
+    "^\\.renovate/sync-template-version\\.sh$"
+  ],
   "postUpgradeTasks": {
     "commands": [
       ".renovate/sync-template-version.sh"