| * feat(tmpl): added fetchSecretValue template function
This adds a tmpl `fetchSecretValue` and `expandSecretRefs` function by:
- Adding:
    - `expandSecretRefs` function in tmpl package that uses vals
    package to fetch secrets
    - `fetchSecretValue` function in tmpl package like below but for
    single string value
    - gomock for tests purpose
- Changing:
    - move init of vals package to function (so the same instance can be used for template values and rendering the whole template)
* doc(secret): added doc how to use new tmpl methods
Added example usage of `fetchSecretValue` and `expandSecretRefs` | ||
|---|---|---|
| .. | ||
| remote-secrets.md | ||
| shared-configuration-across-teams.md | ||
| writing-helmfile.md | ||