Bump node-fetch and bpmn-to-image in /src/main

Bumps [node-fetch](https://github.com/node-fetch/node-fetch) to 2.7.0 and updates ancestor dependency [bpmn-to-image](https://github.com/bpmn-io/bpmn-to-image). These dependencies need to be updated together.


Updates `node-fetch` from 2.6.1 to 2.7.0
- [Release notes](https://github.com/node-fetch/node-fetch/releases)
- [Commits](node-fetch/node-fetch@v2.6.1...v2.7.0)

Updates `bpmn-to-image` from 0.6.1 to 0.7.0
- [Release notes](https://github.com/bpmn-io/bpmn-to-image/releases)
- [Changelog](https://github.com/bpmn-io/bpmn-to-image/blob/main/CHANGELOG.md)
- [Commits](bpmn-io/bpmn-to-image@v0.6.1...v0.7.0)

---
updated-dependencies:
- dependency-name: node-fetch
  dependency-type: indirect
- dependency-name: bpmn-to-image
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>