feat: allow inline yaml config instead of string literal (#43)

### Description of the change

Allow to insert the act_runner config as yaml into the chart values.

### Benefits

Yaml editor will report yaml errors, instead of the deployed runner.

### Possible drawbacks

No limitations, string config works like before.

### Applicable issues

N/A

### Additional information

Usage like this, just omit the block scalar token

```yaml
enabled: true
statefulset:
  actRunner:
    # See full example here: https://gitea.com/gitea/act_runner/src/branch/main/internal/pkg/config/config.example.yaml
    config:
      log:
        level: debug
      cache:
        enabled: false
      container:
        valid_volumes:
        - /var/run/docker.sock
        options: -v /var/run/docker.sock:/var/run/docker.sock

## Specify an existing token secret
##
existingSecret: "runner-token2"
existingSecretKey: "token"

## Specify the root URL of the Gitea instance
giteaRootURL: "http://192.168.1.2:3000"
```

I do not like the regex test approach, but I didn't come up with a better one. I wish that I can parse the nested yaml in the helm tests.

### ⚠ BREAKING

N/A

### Checklist

- [x] Helm templating unittests are added (required when changing anything in `templates` folder)
- [x] All added template resources MUST render a namespace in metadata

Reviewed-on: https://gitea.com/gitea/helm-actions/pulls/43
Reviewed-by: DaanSelen <daanselen@noreply.gitea.com>
Co-authored-by: Christopher Homberger <christopher.homberger@web.de>
Co-committed-by: Christopher Homberger <christopher.homberger@web.de>

unittests/helm/config-act-runner.yaml

@@ -42,3 +42,27 @@ tests:
             runner:
               labels:
                 - "ubuntu-latest"
+  - it: renders a ConfigMap with inline yaml
+    template: templates/config-act-runner.yaml
+    set:
+      enabled: true
+      statefulset:
+        actRunner:
+          config:
+            container:
+              valid_volumes:
+                - /var/run/docker.sock
+              options: -v /var/run/docker.sock:/var/run/docker.sock
+    asserts:
+      - hasDocuments:
+          count: 1
+      - containsDocument:
+          kind: ConfigMap
+          apiVersion: v1
+          name: gitea-unittests-actions-act-runner-config
+      - matchRegex:
+          path: data["config.yaml"]
+          pattern: '(?m)^\s*options:\s*-v /var/run/docker.sock:/var/run/docker.sock\s*$'
+      - matchRegex:
+          path: data["config.yaml"]
+          pattern: '(?m)^\s*valid_volumes:\s*\n\s*-\s*/var/run/docker.sock\s*$'