* ci: run `npm ci` to install and ignore scripts
`npm ci` is meant to be used in CI environments and the scripts are ignored to prevent e.g. Husky
from being installed in the CI environment. See https://docs.npmjs.com/cli/v7/commands/npm-ci.
* ci: run `npm ci` to install and ignore scripts in the Dockerfile
The action's image is now based on alpine, which reduced drastically it's size. The previous compressed size was ~352 MB, now it's only ~56 MB.
Resolves#37
