Bump eventsource from 1.1.0 to 1.1.2 in /demo

Bumps [eventsource](https://github.com/EventSource/eventsource) from 1.1.0 to 1.1.2.
- [Release notes](https://github.com/EventSource/eventsource/releases)
- [Changelog](https://github.com/EventSource/eventsource/blob/master/HISTORY.md)
- [Commits](EventSource/eventsource@v1.1.0...v1.1.2)

---
updated-dependencies:
- dependency-name: eventsource
  dependency-type: indirect
...

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Author: dependabot[bot]