Improve deploying to GHPages

## What we have now

We have now script to deploy the project to "Github Pages":
`npm run deploy-to-ghpages`
See more at https://github.com/angular-schule/angular-cli-ghpages

## What we need
What we need now is to be able to deploy only the last release (the last release tag).
For example, it would be nice to specify the commit hash to deploy, something like this:
`npm run deploy-to-ghpages -commit [commit_hash] `
or to specify the app version to deploy, like this:
`npm run deploy-to-ghpages -version [version_number] `
Or maybe just to deploy somehow always the last version. It depends on what will be easier to make.

**The main goal** is that no "unreleased" version is going to be deployed.

Also the README.md should be updated accordingly.