docs: update README.md with prefix tag docs (#284)

Author: anthonylim24

README.md

@@ -230,6 +230,16 @@ npm run release -- --dry-run
 standard-version --dry-run
 ```
 
+### Prefix Tags
+
+If you would like to prefix your tags with something, you can do so with the `-t` flag.
+
+```sh
+standard-version -t @scope/package\@
+```
+
+This will prefix your tags to look something like `@scope/[email protected]`
+
 ### CLI Help
 
 ```sh