Use new substitution feature to switch between serial codes

src/Tools/psxcdgen_ex/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "psxcdgen_ex"
-version = "0.2.2"
+version = "0.2.3"
 edition = "2021"
 
 [profile.release]

src/Tools/tool_helper/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "tool_helper"
-version = "0.9.1"
+version = "0.9.2"
 edition = "2021"
 
 [profile.release]

src/Tools/tool_helper/src/lib.rs

@@ -213,6 +213,14 @@ pub fn input_to_vec(input: Input) -> Result<Vec<u8>, Error> {
 }
 
 pub fn read_file(file_path: &PathBuf) -> Result<Vec<u8>, Error> {
+    if let Some(ext) = file_path.extension() {
+        if ext == "subst" {
+            // File needs substitution!
+            let file_content = read_file_to_string(file_path)?;
+            return Ok(string_with_env_from(&file_content).into_bytes());
+        }
+    }
+
     match std::fs::read(file_path) {
         Ok(data)   => Ok(data),
         Err(error) => create_file_read_error(file_path, error),