Exclude examples from workspace
Fixes
```
Error: Error during execution of `cargo metadata`: error: current package believes it's in a workspace when it's not:
current:   /__w/lumen/lumen/examples/spawn-chain/Cargo.toml
workspace: /__w/lumen/lumen/Cargo.toml
```
@@ -52,6 +52,10 @@ default-members = [
"runtimes/full",
]
+exclude = [
+ "examples"
+]
+
[profile.release]
# Experimentally determined to give the smallest size out of all `opt-level`s (0-3,'s','z') and
# `lto`s (true and false) for `examples/spawn-chain/pkg/spawn_chaing_bg.wasm`
