Extend script runners

[ravloony]

I extended the script runners to:

• automatically update the file permissions in src/ to the current user from outside docker, to avoid permissions problems due to docker running as root.
• remove redundancy between mix and run by having mix pass through to run
• add an npm command that calls npm in the right directory.

[nicbet]

@ravloony Thanks for the PR! I really like the consolidation of mix to call run, and the added npm shortcut.

As for the permissions fix in the run script, I believe a better way around this would be to either map UIDs in the container to match or build the container with the proper UIDs. My past experience with chown on the docker file system is incredibly disruptive (creates a new layer for each changed file/permission) and really slow in the long run.

https://jtreminio.com/blog/running-docker-containers-as-current-host-user/ Has some fantastic discussion around the issue.