implement no_std event listeners

implement no_std event listeners

.github/workflows/ci.yml

@@ -29,6 +29,10 @@ jobs:
         if: startsWith(matrix.rust, 'nightly')
         run: cargo check -Z features=dev_dep
       - run: cargo test
+      - name: Install cargo-hack
+        uses: taiki-e/install-action@cargo-hack
+      - run: rustup target add thumbv7m-none-eabi
+      - run: cargo hack build --target thumbv7m-none-eabi --no-default-features --no-dev-deps
 
   msrv:
     runs-on: ubuntu-latest

Cargo.toml

@@ -15,7 +15,16 @@ categories = ["asynchronous", "concurrency"]
 exclude = ["/.*"]
 
 [dependencies]
-parking = "2.0.0"
+concurrent-queue = { git = "https://github.com/smol-rs/concurrent-queue.git", default-features = false }
+parking = { version = "2", optional = true }
+
+[target.'cfg(loom)'.dependencies]
+loom = "0.5"
+
+[features]
+default = ["std"]
+std = ["parking", "concurrent-queue/std"]
 
 [dev-dependencies]
+futures = { version = "0.3", default-features = false, features = ["std"] }
 waker-fn = "1"