Update Serve command (#116)

Co-authored-by: Martijn Laarman <[email protected]>

README.md

@@ -63,7 +63,7 @@ Through the `serve` command you can continuously and partially compile your docu
 
 ```bash
 docker run -v "./.git:/app/.git" -v "./docs:/app/docs" -v "./.artifacts:/app/.artifacts" \
-  --expose 8080 ghcr.io/elastic/docs-builder:edge serve
+  -p 8080:8080 ghcr.io/elastic/docs-builder:edge serve
 ```
 
 Each page is compiled on demand as you browse http://localhost:8080 and is never cached so changes to files and 
@@ -148,4 +148,4 @@ The resulting binary `./.artifacts/publish/docs-builder` will run on machines wi
 To test performance it's best to build the binary and run outside of docker:
 
 For refence here's the `markitpy-doc` docset (50k markdown files) currently takes `14s` vs `several minutes` compared to 
-existing surveyed tools
+existing surveyed tools