docs(sourcemap): add trailing newline to README (#5539)

For consistency with our `.editorconfig`.

crates/oxc_sourcemap/README.md

@@ -1,4 +1,4 @@
 The sourcemap implement port from [rust-sourcemap](https://github.com/getsentry/rust-sourcemap), but has some different with it.
 
 - Encode sourcemap at parallel, including quote `sourceContent` and encode token to `vlq` mappings.
-- Avoid `Sourcemap` some methods overhead, like `SourceMap::tokens()`.
+- Avoid `Sourcemap` some methods overhead, like `SourceMap::tokens()`.