release: 0.7.3 (#52)

### Description

This release updates the Backstage plugin configuration schema to add
support for `apiToken`.

```yaml
pagerDuty:
   apiToken: u+a81u12y4ax
```

The latest release of the backend plugin
([0.2.0](https://github.com/PagerDuty/backstage-plugin-backend/releases/tag/0.2.0))
required a schema change for the plugin to start successfully. It does
not introduce changes to the frontend plugin but this release makes sure
that the schemas match.

### Type of change

- [ ] New feature (non-breaking change which adds functionality)
- [x] Fix (non-breaking change which fixes an issue)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)

### Checklist

- [x] I have performed a self-review of this change
- [x] Changes have been tested
- [x] Changes are documented
- [x] Changes generate *no new warnings*
- [x] PR title follows [conventional commit
semantics](https://www.conventionalcommits.org/en/v1.0.0/)

If this is a breaking change 👇

- [ ] I have documented the migration process
- [ ] I have implemented necessary warnings (if it can live side by
side)

## Acknowledgement

By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.

**Disclaimer:** We value your time and bandwidth. As such, any pull
requests created on non-triaged issues might not be successful.

config.d.ts

@@ -24,5 +24,10 @@ export interface Config {
      * @visibility frontend
      */
     eventsBaseUrl?: string;
+    /**
+     * Optional PagerDuty API Token used in API calls from the backend component.
+     * @visibility frontend
+     */
+    apiToken?: string;
   };
 }