Add initial session / systemd integration

Cargo.lock

@@ -813,6 +813,7 @@ dependencies = [
  "clap",
  "keyframe",
  "profiling",
+ "sd-notify",
  "smithay",
  "smithay-drm-extras",
  "tracing",
@@ -1186,6 +1187,12 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e1cf6437eb19a8f4a6cc0f7dca544973b0b78843adbfeb3683d1a94a0024a294"
 
+[[package]]
+name = "sd-notify"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "621e3680f3e07db4c9c2c3fb07c6223ab2fab2e54bd3c04c3ae037990f428c32"
+
 [[package]]
 name = "sharded-slab"
 version = "0.1.4"