fix: update serde dependency to include derive feature in Cargo.toml

[davehorner]

simple fix, this example requires the derive macro.

[davehorner]

that fixes it compiling; it doesn't work exactly. maybe not an example? code doesn't compile without derive.
2025-03-22T10:55:57.889587Z WARN cosmic_text::font::system: failed to load font 'GB18030Bitmap'
2025-03-22T10:55:57.899802Z ERROR changelog: no GITHUB_TOKEN variable was set

[hecrj]

Thanks!

The example needs the GITHUB_TOKEN env variable to be set, as the error you pasted says.