Add eas.json contents as step output

### Description of the feature
The action could output the eas.json contents so it can be reused by other steps

### Motivation
I would like to use `expo publish` to the production release channel

### Additional context
This is my current workaround:

```
- name: 🏗 Setup Expo and EAS
uses: expo/expo-github-action@v7

- name: 📦 Install dependencies
run: yarn install

- name: 🏗 Release channel
uses: sergeysova/jq-action@v2
id: releaseChannel
with:
cmd: 'jq .build.production.releaseChannel eas.json -r'

- name: 🚀 Publish app
run: expo publish --non-interactive --release-channel=${{ steps.releaseChannel.outputs.value }}
```

Suggested workflow:

```
- name: 🏗 Setup Expo and EAS
uses: expo/expo-github-action@v7
id: expo

- name: 📦 Install dependencies
run: yarn install

- name: 🚀 Publish app
run: expo publish --non-interactive --release-channel=${{ steps.expo.eas.build.production.releaseChannel }}
```