false positive error on `secrets` context access in forks

For a workflow that accesses secrets:

```yml
- name: "publish npm"
uses: "./.github/actions/publish-npm"
env:
NPM_TOKEN: "${{ secrets.NPM_TOKEN }}"
```

The extension is very helpful in checking if the secret `NPM_TOKEN` is actually defined or not.
However, it only checks secrets defined in the same repository (I suspect `origin` remote), and reports a false-positive error if it was defined in `upstream`, and `origin` is actually pointing to a fork:

> Context access might be invalid: NPM_TOKEN

**Expected behavior**

All remotes to be checked for secrets, not just `origin`, and the error is no longer reported.

**Screenshots**

**Extension Version**
`v0.26.3`

Start by locating the extension's validation of GitHub Actions secrets and how it determines the repository or remotes to inspect. Reproduce the fork-and-upstream scenario described in the issue, then verify that a secret defined upstream no longer produces a false-positive context-access error.

索引モデルが issue の本文から書いたものです。