More dependencies updates and security fixes

This is a maintenance release which updates some of the dependencies.

Some of these updates include security fixes. Specifically:

• upgraded set-value dependency to address "Prototype Pollution" vulnerability.
• upgraded acorn dependency to address "Regular Expression Denial of Service" vulnerability.

The way this server works should not have changed but more testing in real-world application is still a sensible thing to do before updating the rshiny-template's Dockerfile to use this new version.

PR: #4
Ticket: https://trello.com/c/PLR5Dft2