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All the other crates in egui have serde as an optional dependency -
which is great! But sadly egui_extras unconditionally includes it, which
adds a bunch of code to stuff that may not care for it. This PR gates
serde support behind a new `serde` feature.
This is a breaking change; if that's undesirable then we can add it as a
default feature instead, though that wouldn't match any of the other
crates.
* Add syntax highlighing feature to egui_extras
Enable "syntect" feature for great syntax highlighting of any language.
If not a simple fallback is used that works fine for C++, Rust, Python
* Check --no-default-features of egui_extras on CI
* spelling
* Fix building egui_extras without additional features
