Describe how to update the frontend in README

[christoph-maurer]

Proposal for the README of database and metabase:

Update the dependencies

First, the procedure is described for the frontend, then for the backend. package.json lists the dependencies. ^ indicates that the major version is locked and updates are only allowed for minor versions and patches. Use ~ instead of ^ if you want to allow only patches. They usually include the security updates. yarn.lock states all details about the installed versions. Run make upgrade. Take a look at the changes in package.json and yarn.lock and commit them. Run make outdated. Ignore packages which are outdated, but are not yet in long-term support. Update for example typescript with yarn add -D typescript@latest. Run yarn build. This target is defined in package.json in the section scripts. Run make down build up. down is important to prune anonymous containers which include cache. Test the frontend in develop. If it works fine, you can commit your changes and proceed to deploy them.

For the backend, the procedure is the same except for the following changes: Use make update instead of make upgrade. Use make outdated-packages instead of make outdated.