Fix package version in lock file on publish (#1216)

After we publish a new version of the package, the `package-lock.json`
file is always out-of-sync, containing the old version number of the
package until `npm install` is run.

Run `npm install` before the Git commit step so that the lock file is
updated with the latest version.

Author: tombruijn

mono.yml

@@ -2,3 +2,5 @@
 language: nodejs
 repo: "https://github.com/appsignal/appsignal-nodejs"
 npm_client: "npm"
+git-commit:
+  pre: "npm install"