docs: document commit-all flag with example (#127)

Author: JaKXz

README.md

@@ -111,6 +111,15 @@ standard-version --no-verify
 
 If you have your GPG key set up, add the `--sign` or `-s` flag to your `standard-version` command.
 
+### Committing generated artifacts in the release commit
+
+If you want to commit generated artifacts in the release commit (e.g. [#96](https://github.com/conventional-changelog/standard-version/issues/96)), you can use the `--commit-all` or `-a` flag. You will need to stage the artifacts you want to commit, so your `release` command could look like this:
+
+```json
+"prerelease": "webpack -p --bail",
+"release": "git add <file(s) to commit> && standard-version -a"
+```
+
 ### CLI Help
 
 ```sh