Add required info to embassy-sync package

Updates the README.md based on embassy-futures structure.

embassy-sync/Cargo.toml

@@ -2,6 +2,16 @@
 name = "embassy-sync"
 version = "0.1.0"
 edition = "2021"
+description = "no-std, no-alloc synchronization primitives with async support"
+repository = "https://github.com/embassy-rs/embassy"
+readme = "README.md"
+license = "MIT OR Apache-2.0"
+categories = [
+    "embedded",
+    "no-std",
+    "concurrency",
+    "asynchronous",
+]
 
 [package.metadata.embassy_docs]
 src_base = "https://github.com/embassy-rs/embassy/blob/embassy-sync-v$VERSION/embassy-sync/src/"