Removes `egui_assert` etc and replaces it with normal `debug_assert`
calls.
Previously you could opt-in to more runtime checks using feature flags.
Now these extra runtime checks are always enabled for debug builds.
You are most likely to encounter them if you use negative sizes or NaNs
or other similar bugs.
These usually indicate bugs in user space.
* 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
