Add missing mock function

Description

This pr adds mock for setCamera.

Related Issue

Motivation and Context

Unit test failed because of missing setCamera mock function in https://github.com/owncloud/web-app-dicom-viewer/pull/56.

⎯⎯⎯⎯⎯⎯ Unhandled Errors ⎯⎯⎯⎯⎯⎯

Vitest caught 1 unhandled error during the test run.
This might cause false positive tests. Resolve unhandled errors to make sure your tests are not affected.

⎯⎯⎯⎯ Unhandled Rejection ⎯⎯⎯⎯⎯
TypeError: this.viewport.setCamera is not a function
 ❯ Proxy.setZoom src/App.vue:630:21
    628|       }
    629| 
    630|       this.viewport.setCamera(newCamera)
       |                     ^
    631|       this.viewport.render()
    632|     },
 ❯ Proxy.mounted src/App.vue:263:12

This error originated in "tests/unit/App.spec.ts" test file. It doesn't mean the error was thrown inside the file itself, but while it was running.
The latest test that might've caused the error is "should fetch overlay metadata when the url is provided". It might mean one of the following:
- The error was thrown, while Vitest was running this test.
- If the error occurred after the test had been completed, this was the last documented test before it was thrown.

Types of changes

[ ] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)
[x] Tests only (no source changes)

Checklist:

[ ] Code changes
[x] Unit tests added
[ ] Acceptance tests added

owncloud / web-app-dicom-viewer

Add missing mock function #59

Description

Related Issue

Motivation and Context

Types of changes

Checklist:

Quality Gate passed