Bump to 0.4.0. (#59)

diff --git a/Cargo.lock b/Cargo.lock
index 2f4d69c..b99aed5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2027,7 +2027,7 @@
 
 [[package]]
 name = "skywalking-php"
-version = "0.4.0-dev"
+version = "0.4.0"
 dependencies = [
  "anyhow",
  "axum",
diff --git a/Cargo.toml b/Cargo.toml
index 60c682f..8a79856 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -21,7 +21,7 @@
 
 [package]
 name = "skywalking-php"
-version = "0.4.0-dev"
+version = "0.4.0"
 authors = ["Apache Software Foundation", "jmjoy <jmjoy@apache.org>", "Yanlong He <heyanlong@apache.org>"]
 description = "Apache SkyWalking PHP Agent."
 edition = "2021"
diff --git a/dist-material/LICENSE b/dist-material/LICENSE
index c0f02d4..51c24fc 100644
--- a/dist-material/LICENSE
+++ b/dist-material/LICENSE
@@ -224,7 +224,7 @@
     https://crates.io/crates/prost-types/0.11.6 0.11.6 Apache-2.0
     https://crates.io/crates/scripts/0.0.0 0.0.0 Apache-2.0
     https://crates.io/crates/skywalking/0.6.0 0.6.0 Apache-2.0
-    https://crates.io/crates/skywalking-php/0.4.0-dev 0.4.0-dev Apache-2.0
+    https://crates.io/crates/skywalking-php/0.4.0 0.4.0 Apache-2.0
     https://crates.io/crates/sync_wrapper/0.1.1 0.1.1 Apache-2.0
 
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