As reported in RHDHBUGS-200, it would be nice if RHDH Local could allow users to provide and mount their npmrc file, so that they don't need to modify the Compose file manually.

Acceptance Criteria

• It should allow users to specify a local npmrc file to mount in the install-dynamic-plugins container
• It should treat the npmrc file as optional, i.e., it should not fail if the file does not exist
• It should set the NPM_CONFIG_USERCONFIG env var in the install-dynamic-plugins container if the file is mounted. Otherwise, this env var should not be set
• It should update the docs

NOTES:

• Added a dependency on RHIDP-4263, as this will allow for a better way to provide custom config files to the containers.
• Priority set to Minor based on the priority of RHDHBUGS-200, and also because there is a (not ideal) workaround.