Update rfd requirement from 0.14 to 0.15 (#86)

Updates the requirements on [rfd](https://github.com/PolyMeilex/rfd) to permit the latest version.
- [Release notes](https://github.com/PolyMeilex/rfd/releases)
- [Changelog](https://github.com/PolyMeilex/rfd/blob/master/CHANGELOG.md)
- [Commits](https://github.com/PolyMeilex/rfd/compare/0.14.0...0.15.0)

---
updated-dependencies:
- dependency-name: rfd
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Cargo.toml

@@ -14,7 +14,7 @@ chrono = "0.4"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 eframe = "0.28"
-rfd = "0.14"
+rfd = "0.15"
 sha2 = "0.10"
 rusttype = "0.9"
 futures = "0.3"