fix: reduce size (#395)

```diff
du -h swc_plugin_css_modules.wasm
- 832K    swc_plugin_pre_paths.wasm
+ 576K    swc_plugin_pre_paths.wasm
```

Author: SevereCloud

Cargo.toml

@@ -7,8 +7,16 @@ edition = "2021"
 crate-type = ["cdylib", "rlib"]
 
 [profile.release]
+# This removes more dead code
+codegen-units = 1
 lto = true
 
+# Optimize for size
+opt-level = "s"
+
+# Strip debug symbols
+strip = "symbols"
+
 [dependencies]
 
 pathdiff = "0.2"