Enable alloc feature in with-allocator

As the crate name suggests `with_allocator` requires the "alloc" feature
to be enabled.

Author: tcharding

embedded/with-allocator/Cargo.toml

@@ -11,7 +11,7 @@ cortex-m-rt = "0.6.10"
 cortex-m-semihosting = "0.3.3"
 panic-halt = "0.2.0"
 alloc-cortex-m = "0.4.1"
-bech32 = { path="../../", default-features = false }
+bech32 = { path="../../", default-features = false, features = ["alloc"] }
 
 [[bin]]
 name = "with-allocator"