Add debug-widget-callstack and debug-interactive-widgets features

- they need to be separate, both on at once is too much

    --features debug-widget-callstack
      Show callstack for the current widget on hover if all modifier keys
      are pressed down

    --features debug-interactive-widgets
      Show an overlay on all interactive widgets

    Notes:
    - debug-widget-callstack asserts `egui:callstack` feature when enabled
    - Only works in debug builds, compile error w/ release builds

crates/notedeck_chrome/Cargo.toml

@@ -42,6 +42,8 @@ path = "src/preview.rs"
 [features]
 default = []
 profiling = ["notedeck_columns/puffin", "puffin", "puffin_egui"]
+debug-widget-callstack = ["egui/callstack"]
+debug-interactive-widgets = []
 
 [target.'cfg(target_os = "android")'.dependencies]
 android_logger = "0.11.1"