Check `egui_extras --all-features` on CI (#3019)

* Check egui_extras --all-features on CI

* Fix egui_extras with `datepicker` feature

.github/workflows/rust.yml

@@ -53,6 +53,12 @@ jobs:
           command: check
           args: --locked --all-features --all-targets
 
+      - name: check egui_extras --all-features
+        uses: actions-rs/cargo@v1
+        with:
+          command: check
+          args: --locked --all-features --all-targets -p egui_extras
+
       - name: check default features
         uses: actions-rs/cargo@v1
         with:

crates/egui_extras/Cargo.toml

@@ -44,7 +44,7 @@ serde = { version = "1", features = ["derive"] }
 #! ### Optional dependencies
 
 # Date operations needed for datepicker widget
-chrono = { version = "0.4", optional = true, default-features = false, feature = [
+chrono = { version = "0.4", optional = true, default-features = true, feature = [
   "js-sys",
   "wasmbind",
 ] }